In the bookshop, Mr Crime Writer, with his word processor... Peter Guttridge gets on the trail of a suspicious bunch of characters found lurking in mysterious circumstances.

Noon, Saturday. The Mysterious Bookshop on Marylebone High Street, a mile from 221b Baker Street, national shrine for Sherlock Holmes aficionados. The floor to ceiling shelving is groaning with just about every crime book in print - and the shopfloor is heaving with many of the people who wrote them. A positive who's who of whodunnit, whydunnit and howdunnit writers. The group name might be a conspiracy of them.

Keith Miles, chairman of the Crime Writers Association, surveys the crowded shop in wonder. "I've never seen so many crime writers in captivity in one place before," he says. Given the range of crimes they have invented and written about between them, that means that assembled here are some of the sickest minds in Britain.

You wouldn't think it to look at them as they chat happily, quaff champagne and wait their turn to sign their books, aware of the old authors' dictum: a signed book is a sold book (since it can't be returned to the publishers). Hard-boiled is rubbing shoulders with "cosy" crime, young Turks with the old-established, the serious with the jokey.

"Crime fiction now covers everything from blood and guts to cucumber mousse," Natasha Cooper says. (She is cucumber mousse "with a sprinkling of Parmesan".) "Crime fiction has become a very broad church," says Ralph Spurrier, who runs Post-Mortem, a thriving mail-order service for hardback crime fiction. "Historical crime fiction, for example, seems to be on the increase."

Indeed, looking along the shelves, you can see detectives opening up offices in almost every period of history, from the Roman Empire to Renaissance Italy and on down the centuries.

Clare Francis has just finished her signings; the tall, bearded Ed McBain, who has flown in from New York for the launch, is pen-in-hand contemplating a high pile of Nocturne, his latest 87th precinct police procedural. Celebrated British crime writers Ian Rankin, John Harvey, Liza Cody, Sarah Dunant and Mike Phillips are in the crowd. Colin Dexter is coming later. Minette Walters is supposed to be here. She started out but apparently went home because of fog - not quite what you expect from a writer of such strong chillers.

This Mysterious Bookshop launch is just one more proof that crime fiction is booming in Britain. Mid-list authors present today might complain that advances are shrinking and you can't make a living from it, but more crime books than ever are being published and crime fiction remains the most popular genre among library users.

Mike Stotter, editor of the crime magazine Shots In The Dark, says: "There are 183 new titles coming out over the next six months. That works out at one book published every 18 to 20 hours. I don't know what that is doing to advances, but it's good news for readers."

With the exception of a few big names - such as Ruth Rendell, PD James, Reginald Hill and Michael Dibdin - British crime writers have often seemed to be in the shadow of the US big guns: McBain, Elmore Leonard, James Ellroy. However, a major reason The Mysterious Bookshop has opened is to meet the increasing demand in America for British crime writing.

The bookshop's owner, dapper Otto Penzer - a legendary figure in American mystery writing circles - already has two famous Mysterious Bookshops in New York and Los Angeles.

"But I needed to open one over here too," he says. "There is such an appetite for British crime writing in the States and I could never get enough books to meet the demand for first editions. Now I can get them through this shop. As little as five years ago it was traditional stuff - Dexter, Rendell, PD James - but these talented new writers like Ian Rankin and John Harvey with the noir stuff do very well, too."

There are already two other quality bookshops devoted to crime fiction in London: Maxim Jacobowski's Murder One and, in Covent Garden, Crime In Store, which is partly backed by authors such as John Harvey and Val MacDermid.

Harvey is happy to welcome one more shop: "Any bookshop where I bowl along and they have my book in the window - I'm happy that it's there," he says. "Otto knows what he's doing and I think it will help give a buzz to buying crime books."

Harvey, like most of the writers in the shop, writes a crime series featuring the same central character - Charlie Resnick, a melancholy cop fond of complicated sandwiches and jazz. The supposed limitations of this form and the need for a central character with quirky characteristics is one reason sometimes adduced by editors of the books pages for their unwillingness to cover crime fiction seriously. The conventions of crime fiction, the line goes, make it formulaic, not literary. What can you say about yet another lonely cop with a bad liver, a broken heart and a liking for music?

Harvey disagrees, although he is bringing his series to an end with the next Resnick, the tenth.

"The only thing you have to watch against is lazy writing. First thing on a Monday morning - what can I write now? I know, I'll have Resnick make another sandwich. As for the form - it isn't inhibiting, it's elastic."

Indeed the hot tip for the winner of this year's CWA Gold Dagger, Ian Rankin's Black and Blue, is both the eighth in his Inspector Rebus series and one of the most original novels of the Nineties. Rebus is one of the music-loving cops. Rankin jokes: "He started out liking jazz but then Resnick came along so Rebus developed an interest in Sixties pop music. I wish now that I'd made it early Seventies so I could refer to my vast collection of concept albums."

Rankin and Harvey are among a number of British authors, loosely termed noir writers, who are challenging the best of American crime writing. Fresh faces on this scene include Christopher Brookmyre and Nicholas Blincoe.

However, publisher Jim Driver, who's Do Not Press is one of a number of small independent outfits publishing "cutting edge" British crime fiction, doesn't think Britain's answer to Elmore Leonard will be easily found unless the attitude of booksellers and the media changes.

"They assume the big publishers have their fingers on the pulse but I'm afraid they don't. It's the small, independent publishers who have - we exist only by scraping the cutting edge. The Do Not Press published two out of the three short stories on the CWA Dagger for Best Short Story shortlist in our Fresh Blood 2 collection yet no national newspaper or magazine has yet reviewed the book."

The co-editor of the collection, the multi-award winning Mike Ripley, published his latest novel, That Angel Look, through the Do Not Press. Declaring it would be the last book in the series featuring the witty Fitzroy Maclean Angel, he sold it to Driver for one penny because he preferred being published by him rather than dealing with his original publisher who was showing little interest in it.

As the afternoon wears on, more and more enthusiasts for crime bemoan the blinkered visions of the newspaper books editors who choose regularly to review literary novels of limited interest rather than often better written crime novels.

"Crime novels are first and foremost novels," Keith Miles says. "They follow the same rules of composition as literary novels, concentrating on character and plot."

"We are the inheritors of the 19th century novel," says Alison Joseph, who, unlikely as it sounds, writes a series featuring Sister Agnes, a crime-busting nun. "We and saga writers continue that tradition of dealing with social issues in a strong narrative. Readers look to literary fiction for that and don't find it whilst we continue to tell damned good stories."

However, when Colin Dexter arrives he makes the point that plot is crucial to a good crime novel.

"I did a particular bit of `fine writing' in my second novel, about seagulls wheeling about Morse's head on a seashore. I thought, what a lovely piece of writing. I handed over the manuscript to my editor and when I met her next I asked her if she recalled that portion and didn't she think it was lovely. Yes, she said, lovely. I cut it - it doesn't move the plot along."

Peter Guttridge's debut crime novel, `No Laughing Matter' (Headline), comes out in paperback, price pounds 5.99, on 9 December.