Former shop assistant tipped to win Booker

He has gone from shop assistant to the hottest favourite in the history of the Man Booker Prize. With his novel Cloud Atlas already judged a masterpiece, author David Mitchell is tipped to become the third winner in as many years to be drawn from outside the ranks of established literary heavyweights.

The bookmaker William Hill has installed Mitchell, a one-time salesman at Waterstone's, as the clear front runner at odds of 5-4. The winner will be announced on Tuesday.

Cloud Atlas, a series of interconnected tales in different genres, faces competition from two well-known figures in the literary establishment. Alan Hollinghurst's The Line of Beauty, depicting Britain in the Thatcher years, is listed at 5-2, and Colm Tóibín's The Master, inspired by the life of Henry James, has been given odds of 4-1.

The remaining three, Sarah Hall's The Electric Michaelangelo, Gerard Woodward's I'll Go to Bed at Noon and Achmat Dangor's Bitter Fruit, are thought to have comparatively little chance.

Mitchell's books have only been on the shelves for the past five years, and a win for Cloud Atlas would further the Booker's recent reputation for championing emerging figures, following wins by virtual unknowns for each of the previous two years. DBC Pierre's Vernon God Little won last year and Yann Martel's Life of Pi in 2002.

It is Mitchell's second time on the Booker short-list. He last appeared in 2001 with number9dream, when he was beaten to the title by Peter Carey, but he remains little known to the majority of readers.

The Booker's emphasis on up-and-coming writers has drawn some criticism - much of this year's long-list was made up of first- or second-time writers. Man Booker has even launched an international prize to reward longer-term literary achievements, which will be awarded biennially from next year.

The judges, led by their chairman Chris Smith MP, meet for the first time on Tuesday since the short-list was made public a month ago, with the result announced at a dinner of the great and good in the publishing world.

Organisers of this year's ceremony, which takes place at the Royal Horticultural Halls in Pimlico, London, for the first time, will be hoping to end a two-year row about the venue. It has been held at the British Museum for the two previous years, but guests were angered by the poor sound quality at the event with many unable to understand the winners' speeches.

The strands of Mitchell's novel include a 19th-century Pacific crossing through the diaries of an American notary, a 1970s investigation by a reporter into a scientist's death and the story of a genetically engineered fast-food waitress, set a century in the future.

The biggest prize in the UK's literary landscape is worth a fortune in extra sales to the winning author, on top of the £50,000 sum he or she will collect.

If recent winners' experience is anything to go by, he can expect to sell at least half a million copies, which would be a 60-fold increase on his current sales. Last year's winner, DBC Pierre, sold that many with Vernon God Little, while Yann Martel in 2002 is estimated to have shifted 1.75 million copies of The Life of Pi.

Cloud Atlas has seen the biggest benefit of the six nominees, its sales rising by nearly a quarter since the short-list was announced last month.

A win for Mitchell - who is three books into his career - is by no means assured. Although he is favoured by many, the judges may have to opt for a compromise candidate if any of their number are implacably opposed to it. "Cloud Atlas is one of those books that many people love, but if you hate it, you really hate it," as one leading figure in the book trade put it last week.