The advance of special effects has helped science fiction shed its alternative status and become part of the mainstream. Yet, as Charles Shaar Murray discovers, sci-fi is still a form that cherishes its margins To acknowledge the post-millennial primacy of screen over page, the next Man Booker Prize ceremony will be held as part of the London Film Festival . . . Relax, I’m just kidding. Still, that Sci-Fi-London, the Fifth London International Festival of Science Fiction and Fantastic Film, will host not only the Arthur C Clarke Award (the genre’s most prestigious literary prize), but also the Douglas Adams Memorial Debate, does demonstrate two important changes. The first is that, as far as most consumers of science fiction are concerned, the dramatic now takes precedence over the textual. The second is that the "sci-fi" abbre- viation - once despised as a demeaning diminutive used only by outsiders - has become generally acceptable. (True insiders, by the way, distinguish themselves from hoi polloi by pronouncing it "skiffy".)

Whatever you call it, and however it’s pronounced, SF is undergoing a protracted process of redefining its relationship with the mainstream. In a sense, this represents the closing of a circle. Until the 20th century, there was no such thing as "genre fiction": there was simply literature. Jules Verne, Arthur Conan Doyle and H G Wells were no more "genre writers" than were Dickens or Shakespeare: they were simply writers. Like crime and romance, the literature of the fantastic - SF, horror, fantasy and all points in between - became a red-headed stepchild, exiled to the foot of the table and kept at the periphery of the literary family, a safe distance away from the respectable realist novel. Exceptions were rare and grudging: Aldous Huxley’s Brave New World and George Orwell’s Nineteen Eighty-Four were allowed into the canon because of their authors’ previous good behaviour. More recently, J G Ballard, Michael Moorcock and Brian Aldiss have been permitted to work their way in from the margins.

The screen, by contrast, has always been more egalitarian. From Metropolis, King Kong and Frankenstein to Independence Day, The Matrix and beyond, viewers have been far more reluctant to specialise than readers. One truism of the prose-SF-versus-filmed-SF debate is that the author has, for all practical purposes, an unlimited special-effects budget. It is no more expensive for a writer to describe two galaxies colliding in the 35th century than it is to inform readers that a character has put on an overcoat. It wasn’t until the quantum leaps in special effects represented by Stanley Kubrick’s 2001: a space odyssey (1968) and George Lucas’s Star Wars (1977) that it became practical, or affordable, to realise on screen the kind of spectacular cosmic events that were routine in print. The reason J R R Tolkien’s Lord of the Rings took so many years to arrive on screen, despite its long-term popularity, was that it simply wouldn’t have been possible to produce any earlier.

This side of the millennial divide, SF and superhero blockbusters are big business: familiar and welcome fare in cinemas and on TV. The misconceived and slipshod Enterprise may have capsized the once mighty Star Trek franchise, but space opera has remained a constant TV presence with the likes of Farscape, Andromeda, the reimagined Battlestar Galactica and Joss Whedon’s sadly short-lived Firefly (though this was successfully resurrected as the theatrical feature Serenity). SF spectaculars such as Steven Spielberg’s pea-brained War of the Worlds, the Wachowski Brothers’ flawed but intriguing dystopia V For Vendetta and Peter Jackson’s pumped-up tour de force King Kong all have a shareholder-pleasing bums-on-seats factor.

So where does this leave toilers in the salt mines of print SF - agog at new opportunities created by the screen-driven expansion of the field or resentful at being elbowed out of their comfy ghetto patch? Or is it simply business as usual?

Well, many skiffy stars have chosen to explore pastures (galaxies?) new. Some, such as Paul McAuley, have stepped sideways to the technothriller (though McAuley himself plans to return to SF), while Michael Marshall Smith, temporarily divesting himself of his second surname, has essayed the darker shades of noir. Neal Stephenson, heir to the original cyberpunk generation led by William Gibson and Bruce Sterling, has moved into the historical novel - hey, the past is the new future! - with his stunning "Baroque Cycle". Gibson himself, with his 2003 novel Pattern Recognition, has remained true to the cyberpunk genre he helped pioneer more than 20 years ago with Neuromancer. Set in 2002, Pattern Recognition is also, technically, a historical novel.

Nevertheless, the two main SF tropes, best summed up by the titles Star Wars and If This Goes On, remain defiantly in place. The former represents space opera in all its forms; the latter extrapolates current social, political and technological trends into dystopic futures both near and far. Fantasy is another subgenre, with influences ranging from the heroic (bad imitations of J R R Tolkien or characters such as Conan the Barbarian) to the dark (vampires, zombies and werewolves, often served up with a healthy garnish of bondage and sadomasochism).

A quick sniff at the current Clarke shortlist - the first ever all-British selection, incidentally, if we allow for Canadian author Geoff Ryman’s long-term UK residency - reveals two upmarket examples of bread-and-butter space op: Alastair Reynolds’s Pushing Ice (Gollancz) and Ken Macleod’s Learning the World (Orbit). The accompanying pair of trend extenders, blasting infotech into the near(ish) future, couldn’t be more different: Charles Stross’s Accelerando (Orbit) is heavy-metal cyberpunk, turning up both density and velocity to perversely enjoyable headache levels; while Ryman’s Air (Gollancz) depicts the im-pact of a technology called Air, which literally puts the internet into your head, on a tiny remote village in a mythical country bord ering China, Tibet and Kazakhstan. Combining classic SF imagineering with Ryman’s characteristically idiosyncratic take on magic realism, it would be the smart and the brave pick to win.

The list also features one mainstream novelist included in a grab for literary respectability: Kazuo Ishiguro’s Never Let Me Go (Faber) lumberingly revisits an SF theme handled rather more stylishly some years ago by Michael Marshall Smith in Spares. Presumably the judges felt it would be a coup either to have Ishiguro there to watch someone else win, or else to give him the gong in preference to any of the skiffy vets.

Among the screen treats at the festival are two alt-history mock-docs: Aleksey Fedorchenko’s First on the Moon, based on the proposition that the Russian space programme predated the First World War; and Kevin Willmott’s CSA, relating events from the Confederate victory in the American civil war to the present day. Carrying the imprimatur of a "Spike Lee Presents" tag, Willmott’s depiction of an America still cheerfully practising slavery is both sardonically witty and eerily plausible.

Elsewhere, Philip Chidel’s Subject Two and James Bai’s Puzzle- head depict mad scientists in isolated settings (the former snowy Montana, the latter post-catastrophic Brooklyn) conducting fiendish experiments on initially uncomprehending subjects. More fun, if somewhat longueur-ridden, is Gen Sekiguchi’s Survive Style 5+, a multi-stranded exercise in Japanese weirdness that earns major B-movie points for stunt-casting Vinnie Jones and Sonny Chiba.

If the programme of the Sci-Fi-London festival proves anything it is that, no matter how mainstream SF gets, it still cherishes its margins. The fantastic may prove harder to domesticate than Hollywood thinks.