I first read Billion Year Spree by mistake. It was the mid-1970s, and I was working a shift at my local public library. The pay was low, but the company was good and I managed to get first pick of the new science fiction novels as they arrived.

When a new Brian Aldiss hardback appeared, I made sure I was first in the queue - only to find that it wasn't a novel, but a history of science fiction itself. Disappointed, I ploughed into it anyway and discovered that it wasn't the dry tome I had feared but a witty, intensely personal discussion of the genre.

This was an important moment for me. Science fiction was my core literary interest, yet it was roundly dismissed by those insistent on feeding me a diet based firmly on Thomas Hardy and D.H. Lawrence. It was deemed hardly better than the cowboy yarns and medical romances I spent so much time re-shelving. Now I had some ammunition: a scholarly review of science fiction that gave it not only a respectable pedigree but reasons for being taken seriously.

Today it would probably be labelled critical analysis, but the flavour of Aldiss' 1973 text is much more that of a personal odyssey - one that places Mary Shelley's Frankenstein (1818) at the root of the genre and builds a family tree forward from that point, by way of Edgar Allan Poe, Jules Verne, H.G. Wells and Olaf Stapledon, to the strange new worlds of John Wyndham and J.G. Ballard, Robert Heinlein and James Blish, Isaac Asimov and Arthur C. Clarke.

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These new worlds, and their relevance to contemporary society, are described especially vividly, not least because Aldiss personally knew many of those he was writing about. Most significantly, he was already a successful science-fiction author, and wrote about the genre from the inside as though describing a living thing.

Much later, I came across a collection of essays, The Detached Retina: Aspects of SF and Fantasy (1995), in which Aldiss explains the background to the book. He wrote it without financial support (a real gamble for an author with a family) and drew on his own library. His hope was "by a little clarity of thought, to supersede some of the sillier theories of SF then floating about, and by so doing to focus on the intrinsic nature of the beast". In that, I believe, he was successful.

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It is significant that I am writing this not long after the 40th anniversary of the Apollo 13 launch - a point in history when science and science fiction effectively crossed over. The Apollo 13 events took place while Billion Year Spree was being written, and I believe the book marks an important point where science fiction gained an acknowledged past and entered an increasingly diverse future. On that basis alone, it justifies its place in the pantheon of academic literature, but it is in the humour and wry wickedness of the writing that the book's real magic rests.