Diana Athill won the biography category for her memoirs
Five authors are set to hear who has won the �25,000 Costa Book of the Year Award when the winner is announced in London later.
The contenders are author Sebastian Barry, 91-year-old Diana Athill, first-timer Sadie Jones, poet Adam Foulds and children's author Michelle Magorian.
The writers won individual categories earlier this month.
Barry, who missed out on the Man Booker Prize last year, is the bookmakers favorite with odds of 9/4.
But a William Hill spokesman said Athill - who is third favourite with odds of 3/1 -was the most backed author.
COSTA BOOK AWARDS
Sebastian Barry The Secret Scripture
Diana Athill Somewhere Towards the End
Sadie Jones The Outcast
Adam Foulds The Broken Word
Michelle Magorian Just Henry
Athill is the oldest category-winner in the history of the awards.
Her memoir, Somewhere Towards the End, looks back on her life and the stories, events and relationships that have shaped it.
Booksellers Amazon.co.uk said her title had a sales increase of more than 520% after winning the biography category and she is the strongest-selling title in the running.
Jones is second-favourite at the bookmakers to win the overall award with her debut novel The Outcast.
Magorian, the author of the hugely successful Goodnight Mr Tom, won the children's book award for Just Henry, her first new book in 10 years, and Foulds took the poetry prize for The Broken Word.
The authors have received �5,000 for reaching this stage in the competition.
Barry was nominated for the Man Booker prize last year
"The Costa Book Awards have an excellent track record of recognising and celebrating some of the very best current British writing, and books that can be enjoyed by everyone," said John Derkach, managing director of Costa.
The Costa Book of the Year will be selected by a panel of judges chaired by columnist and broadcaster Matthew Parris and including Rosamund Pike, Michael Buerk, Alexander Armstrong and Andrea Catherwood.
The winner will be announced at an awards ceremony at The Intercontinental Hotel, in London's Park Lane.
Originally established in 1971 by Whitbread, Costa took over the sponsorship of the prize in 2006.
Since the introduction of the Book of the Year award in 1985, it has been won eight times by a novel, four times by a first novel, five times by a biography, five times by a collection of poetry and once by a children's book.
The 2008 Costa Book of the Year was won by AL Kennedy for her fictional book Day.
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