There have long been cautionary tales about scholars whose lust for books has slowly taken over their lives and living quarters.

Take the case of the Victorian dignitary described by his friend John Hill Burton under the blush-saving pseudonym "Archdeacon Meadow". Setting off on one occasion to be examined by a committee of the House of Commons, he promptly disappeared, only to "return penniless, followed by a waggon containing 372 copies of rare editions of the Bible".

His family often had to "search for him on from bookstall unto bookstall, just as the mothers, wives and daughters of other lost men hunt them through their favourite taverns or gambling-houses". Yet Meadow took it calmly when he was outbid at an auction: "I daresay I have ten or 12 copies at home, if I could lay hands on them."

Similar stories and rumours circulate about the great book collectors of recent years. It is a bad sign, for example, when the hunt for rare manuscripts takes precedence over the most rudimentary comfort and basic hygiene, or when even shop-soiled, coffee-stained or water-damaged items are treated like holy relics. It is equally worrying when there are double-backed piles of books in every room in a house, including the bathrooms. And, as yet more volumes encroach on all the space available for eating, living and sleeping, pets, partners and children can find themselves struggling to maintain a precarious foothold.

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The really exceptional book collections require a level of income, leisure and storage space that few academics today can even dream of. Who could hope to match the independently wealthy self-proclaimed "vello-maniac" Sir Thomas Phillipps (1792-1872), whose library of more than 60,000 manuscripts and 50,000 printed books took more than a century to sell off?

Yet some academics do have huge collections of books by any ordinary standards. They take pride in them and see them as essential tools of their trade - if you are researching a wide-ranging topic, it's great to have all the key sources instantly to hand - but also realise that they may satisfy some deep-seated psychological needs. "Some people collect DVDs, some body parts," says Robert Segal, professor of religious studies at the University of Aberdeen. "I collect books. It became clearest when I moved from Lancaster to Aberdeen.

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"The books arrived at Aberdeen the day before me. I'd said I had lots of books, but they agreed to put in extra shelves and kept saying they knew what academics were like. But while I was teaching in summer school, I was summoned to an emergency call from a frantic secretary in Aberdeen: 'I've never seen as many books in my life! Where are we going to put them?' When I arrived, the office was packed, you couldn't walk around, and health and safety wouldn't let them stay in the corridor ... Colleagues were flabbergasted."

Duncan Wu, professor in the English department at Georgetown University in Washington DC, also suspects that he has "an abnormal passion for books - even in my subject area many colleagues have far fewer". When he moved to America from Oxford, his collection - about 300 packing cases, each three quarters full of books - "must have comprised the bulk of what I took with me".

He sees himself as a bibliophile, who collects books from the Romantic period, his main area of research, although these tend to be kept as relics rather than read. But Wu is also an ardent reader, attracted to books "like flies to a piece of rotting meat. I see it just as part and parcel of being a sentient human being - you're interested in what's going on in other people's heads. I buy with the intention of reading them, but many go unread. You overestimate your capacity for reading and think you'll need more than you'll ever read."

James Stevens Curl, honorary senior research fellow at Queen's University Belfast, sees books as "friends, companions and consolers".

"When I go into a house where there are no books," he says, "that house, to me, has no soul, and the people in it are usually boring and empty. Books to me are essential, and I use them every day, for reference or for pleasure (and the two are often the same).

"Books do not take me over, but I have always had to expand my bookshelves in order to accommodate them. If I have finished a project and decide to sell the books collected in relation to that project (usually to make space or to restore the coffers), I invariably miss them and regret the sale.

"I have used every part of the area designated as my study to increase space for books, and I have successfully managed to fit everything in, but then, as an architect, I have the skill to find ingenious ways of creating more spaces for books - perhaps only a small number here or there, but they all add up, and I suppose that one day there will have to be another sale (or perhaps a move to another house, a daunting prospect).

"I have in front of me a complete set of Edmund Burke's Works (shed by the Oblates of St Charles), Sabine Baring-Gould's complete 16-volume Lives of the Saints (which I read for entertainment in matters so improbable they are amusing), Norman Douglas' Old Calabria, the complete Buildings of England series and other treasures to which I turn for enlightenment and solace every day."

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Other academics and scholars recognise themselves as real or recovering bibliomaniacs whose lust for books has occasionally skirted the pathological.

"There certainly have been times when it seemed as though my book collecting was taking over my life," says Arnold Hunt, curator of modern historical manuscripts at the British Library.

"I can identify with the sentiments of (classical scholar) Isaac Casaubon, who wrote in his diary in 1610: 'I have emptied my purse ... I take no thought for my wife, I take no thought for my children. Today I decided that until my wife arrives I will not spend more than a gold sovereign on books - unless something truly rare turns up!' Now, however, I try to take a strictly utilitarian approach to my collecting and to weed my shelves regularly. If a book is useful for my research, it stays; if not, out it goes.

"There have been several occasions when a chance purchase of a second-hand book has set off a research inquiry leading to a publication. For example, a copy of the Reverend Charles Maurice Davies' Unorthodox London, bought for ?1 at a Cambridge book fair about 15 years ago, has resulted in an article and a seminar paper on Davies' journalism and the religious culture of mid-Victorian London."

Lennard J. Davis is professor in the department of English, University of Illinois at Chicago, and the author of Obsession: A History. "I am a bit of a bibliomaniac," he admits, "and I have now got to the point where one buys books one knows will never be read. The desire to own is as great, if not greater, than the desire to read.

"The buying of the book (I do most of that now online) is accompanied by anticipated waiting, the thrill of the arrival, the opening of the package (so akin to Christmas but all the year round), and then the pleasure of holding it and knowing you possess it, that it will join other books on your shelf in some interesting section of your own personal Library of Congress taxonomy. Books are always self-justifying, unlike Rolexes or toasters, because there is a heuristic and scholarly value. But in the end, that is just a screen for the pleasure of possession."

Davis wonders: "Why do I always take too many books on trips? I know I will never read all of them, and I suffer by dragging them along with me like Jesus carrying the cross." He is haunted by "existential guilt" about what he is never going to know and likes to "imagine some island retreat (with mail delivery, of course) in which I would just read, or I posit some long, chronic and wasting but not debilitating illness in which I can finish all the books I've started but never completed or read all the books I've bought but haven't read."

Yet even Davis knows he has not quite crossed the line from an obsessive lust for books to true, pathological bibliomania. "I had a roommate who made the fateful shift from shelves to piles," he recalls. "I think that is a point of no return, and so far I have avoided that step. In his case the house became a series of narrow walkways between larger and more encompassing piles of books."

Books obviously come in many shapes and sizes, so which of them first gives people the book-collecting bug? And what sort of books inspire different individuals with an irresistible desire to purchase them? Philip Youren, manager of the second-hand and remainder department at the main branch of Waterstone's in London, says he knew of one collector who got bored with scholarly tomes about Byzantine history and switched to pop-up books instead. But many people have far more focused interests.

Henry Woudhuysen is professor of English at University College London and co-editor of The Oxford Companion to the Book (to be published by Oxford University Press in January). Since much of his work is on book history, he explains cheerfully, he can legitimately claim to "need any and every book". But although he buys books on the history of English literary scholarship and books once owned by the leading scholars in the field, he also has a number of more personal passions.

One is "dreadful Victorian books with gilt on the covers". A number of 18th-century minor classics such as Oliver Goldsmith's The Vicar of Wakefield, James Thomson's The Seasons and Edward Young's Night Thoughts were reprinted dozens of times in the following century but tend to attract little interest today. Woudhuysen finds them irresistible.

"I feel I need to rescue books that no one wants and give them a home," he says. "I think they are lovely and shouldn't be left in shops where people can do nasty things to them. I look in charity shops and junky places for books that need a home; I can't bear to leave them there even though I've already got two or three copies."

Janine Spencer, director of the Centre for Research in Infant Behaviour at Brunel University, says she became a keen collector only in her twenties but dates her enthusiasm back to when she "was a bit of a precocious reader as a child and remember reading my father's copy of Aleksandr Solzhenitsyn's Cancer Ward. My father's parents were Russian, and I wanted to read something miserable about Russia. Of course, I didn't have a clue what it was about, but I felt grown-up reading it."

Hunt recalls early days "at the second-hand bookstall in Cambridge market. In my time the stall was run by Hugh Hardinge, who would bring out the antiquarian stock early on a Thursday morning. A small group of bibliophiles, including the librarian of Trinity College, the Earl of St Andrews and a mysterious figure known only as 'the man in the cycle helmet', would arrive at about 7am and jostle for position to grab the books as they came out of the boxes."

For Davis, books always "brought the message of adventure, escape from the mundane" into a childhood spent in "drab, working-class, cramped quarters in the Bronx".

And Curl can trace his love of books back even farther, to the time of his earliest memories at the age of two and a half. His grandfather's library, he says, "smelled of old leather, furniture polish and cigars" and was "a wonderland for a child, with marvellous books, some of which my grandfather had collected on his travels in Europe and America, and I remember during the war becoming familiar with the appearance of great cities like Dresden and Berlin that were soon to be very badly damaged.

"My father, too, loved books, and had a library I raided. I became accustomed to reading several books a week, even when very young. So I must have inherited a genetic disposition to love books, the printed page, handsome typography, illustrations and decorations, fine bindings, and all the rest of it."

For Segal, by contrast, aesthetic factors are irrelevant. "I'm the world's biggest philistine," he says. "I probably have only 100 books with illustrations. It's not cover design that interests me, and I don't care about binding or what's on the spine! If it's grubby, written all over or coffee-stained, I don't mind - it's the content that matters.

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"I really want to get inside the head of the author, not just hack into the author's brain to steal information. I imagine myself observing the author writing. Having the book is a sort of magic carpet that takes me back there."

Whenever he travels to give a lecture, Segal makes sure he finds time to visit "the used-book stores". He reports an exhilarating sense of satisfaction if he finds a volume he wants "among the dopey pulp fiction and the books donated to the Cats Protection League".

Trying to summarise the appeal of living among so many books, Segal puts it as follows: "I like it psychologically. It's womb-like. It calms me down.

"I like living in a library - that captures it."

This raises two issues. A big library requires a big house, which may restrict one's choice of residence and force one out into the country or a dodgy part of town. Although Segal admits that he is lucky enough to live "close to campus and in a nice area", he leaves little doubt where his priorities lie. "I wouldn't sacrifice size for location. I couldn't live without my books. When I was reunited with my books, it was like a family reunion. I felt whole again. I would sacrifice clothes or holidays for books without hesitation - they come right after my wife and cats."

We now reach more delicate territory. What about the sexual politics of bibliomania? Woudhuysen has known a number of couples who avidly collect books, but very few women, and he claims that "all space is always fought over by book collectors and the people they live with". When a male collector dies, he adds, "the second-hand dealers often speculate how long it will be before his widow comes to sell his books off".

So let us accept the received wisdom that most "extreme" book collectors are men. Some may be pretty obsessive about it, but there can't be many so dedicated that they literally take food out of their children's mouths to feed their habit or construct impassable barriers of books in their houses.

Nonetheless, if they are heterosexual and looking for a partner, they may have a bit of a problem. There must be plenty of women out there who don't particularly relish the idea of living, or having sex, in a library. Can a lust for books ruin one's love life?

Mary Evans, visiting fellow at the Gender Institute, London School of Economics, sees an element of macho posturing in the overflowing book-lined study.

"Lots of men seem to be in love with the romantic ideal of the academic who proves himself by having books and papers all over the place," she says. "There's an 'I accumulate, therefore I am' pathology at work - as a way of proving you're a real scholar and really doing your job. I had one male ex-colleague whose office was officially made a fire hazard and another who kept every publisher's freebie."

Although she has never come across a household where books had invaded every available surface, Evans does remember "a man who refused to put in central heating because it would take away space for book shelves. I have also known a male academic who was the sole income-earner in his family and felt that books were 'sacred objects', so spending money on them was legitimate, whereas clothes and shoes for wives and children weren't".

The decision to cull her own shelves came when Evans looked through a colleague's library and found it full of "books of the moment" that she had read as an undergraduate 20 years before and were now long forgotten.

"It can be a salutary experience when people retire and try to get rid of their books," she says, "only to find that they are so passe that booksellers and even the local library don't want them." Intellectual fashions have their equivalents of flared trousers or Afro hairstyles. It is probably best to destroy the evidence as soon as possible.

One academic, who asked not to be named, admitted that his collection of books was probably "a factor in the breakdown of my marriage, since my wife asked me to sell many of them".

Nonetheless, he was unrepentant. "Even more than domestic objects," he explained, "books are like people, friends that you live with. So you form attachments and, if people ask you to get rid of them, it's like being forced to cut emotional ties. It's worse than not being allowed to see certain people.

"I have no sympathy with a partner who says, 'Do we really need all the books?' It's like being asked to get rid of a cat or dog."

Whatever the impact on his own domestic life, he is eloquent about why books matter as objects and why it is nice to be surrounded by them: "The places we pass through in reading a book, even a cheapo novel, the damage we do to it, makes it more personal.

"Everyone's experience of reading anything is unique. And anything that reminds us of our own uniqueness is valuable at a time when industrialised societies are geared to reducing us to anonymous units that are indistinguishable from each other."

PRIZE OBSESSIONS

An unusual award for budding bibliophiles or bibliomaniacs is given each year by the Friends of the Goddard Library at Clark University in Worcester, Massachusetts.

The competition was set up by the noted bibliophile Nicholas Basbanes, who still provides some of the funding for the four prizes - two for undergraduates and two for postgraduates.

Students are invited to submit "at least 25 books or similar items (eg, pamphlets, periodicals, broadsides, postcards)". The judges are principally looking for collections that represent "a well-defined theme or field of interest", although they also take account of "the creativity, thoughtfulness and dedication" that have gone into "defining and creating" them.

For Mott Linn, the head of collections management at the Goddard Library, the aim of the Nicholas Basbanes Student Book Collecting Contest is to promote and celebrate "the love of collecting books", as opposed to "just slavishly gathering a lot of books on one subject because your studies require you to".

The latest awards went to collections on the history of philosophy and American literature from the Civil War to the Second World War.

But for Linn, all-time pride of place must go to the material "owned by a graduate student of international development on the subject of tuberculosis sanatoriums".

"While the books alone would have made it the best collection we have seen, what really put it over the top was a box - about the size of a shoebox, but made of archival-quality cardboard - filled with postcards with photos of TB sanatoriums; he had collected them one by one at flea markets."

A THIRST FOR ACQUISITION

A classic account of the book-collector's passion appears in the essay "Unpacking My Library" by the cultural critic Walter Benjamin (1892-1940).

Writing "amid the disorder of torn-open packing cases, breathing in the sawdust-laden air, the floor around me littered with scraps of paper", Benjamin examines the different ways a committed bibliomaniac can build up an impressive treasure house of books: by writing them himself, by inheritance, by skilful tactics at auctions and, simplest of all, by "borrowing followed by failing to return".

When a true collector goes out "in search of books to conquer", claims Benjamin, he plans it like a military campaign. His behaviour "has very little in common with what a student, getting hold of a textbook, or a man of the world, looking for a gift for his lady, or a commercial traveller, in search of something to shorten the next railway journey, does in a bookshop". Indeed, the thirst for acquisition can run so deep that there are stories of "people who became invalids after losing their books".

"Unpacking My Library" was originally delivered as a lecture in 1931. It has recently been reissued, in a new translation by J.A. Underwood, in a Penguin Modern Classics collection One-Way Street and Other Writings, along with essays on translation, photography, violence, hashish, surrealism, Kafka and Proust.

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