By Tim Masters
Entertainment correspondent, BBC News
One fifth of all books sales are made in the six weeks before Christmas
It's become the unofficial start of the Christmas shopping season.
Today has been dubbed "Super Thursday", when more than 800 hardback titles are released at the same time in the UK as publishers vie for a place in December's bestseller lists.
Some of the big names tipped for the top this year include comedian Peter Kay, DJ Chris Evans, TV's Ant and Dec, veteran rocker Ozzy Osbourne and Winnie-The-Pooh.
Already, the bookies are offering odds on likely rivals for the number one slot.
If it's all starting to sound very similar to the music industry's annual race for the top of the Christmas pop charts, that's because it is.
And, when you examine the statistics, it's not hard to see why this is a crucial time for the book industry.
According to Nielsen BookScan figures, one fifth of book sales (by value) are made in the run-up to Christmas.
The biggest selling fiction title last year was J K Rowling's Harry Potter spin-off, The Tales of Beedle the Bard.
The biggest celebrity memoir came from Paul O'Grady - whose 665,000 sales raked in an estimated £6m.
"Predicting which books are going to do well is notoriously difficult," says Andre Breedt, research and development analyst at Nielsen BookScan.
He points out that no-one thought a year ago that the Paul O'Grady book would have been the top seller.
Breedt says that while "Super Thursday" is a recent label, the surge in new books three months before Christmas is nothing new.
"Books tend to have a cyclical lifecycle. For a long time no one really counted them, it's something just something that happened quietly in the background."
According to Nielsen BookScan, which monitors book sales figures, some 2,500 books are being published on 1 October - these include paperbacks, audiobooks and eBooks, not all of which are aimed at the Christmas market.
Last year the figure was around 3,000 books, including 1,000 hardbacks.
'Word of mouth'
So why do publishers tend to agree on 1 October and not a date closer to Christmas like 1 November?
"You risk losing some early sales or not building enough momentum, not getting enough word of mouth, or reviews," explains Breedt. "It is definitely a calculated move.
"You can almost view 1 October as a cut-off point, unless you are very lucky or you have a huge guaranteed hit like Harry Potter."
With three times more than the usual number of books coming out this week, publishers face the challenge of getting their products noticed.
"It's the top few titles that get the massive bulk of sales, so it's very important for a publisher to have one of the books that's lucky," says Benedicte Page, of The Bookseller.
The late Stieg Larsson's final novel is tipped to do well
As well as the celebrity offerings, Page says fiction titles from authors Cecelia Ahern, Stieg Larsson and Audrey Niffenegger (author of The Time Traveler's Wife) are likely to do well.
Carole Tomkinson, from publisher HarperCollins told the BBC: "If you get in the top five slot the retailers give you twice as much space, they push the book, they put it in their ads.
"Our retailers really support the books that are the most successful, and success multiplies success."
Not all of the big titles are released on "Super Thursday". Last month, Dan Brown's Da Vinci Code sequel The Lost Symbol sold more copies in its first 36 hours of UK release than any previous adult hardback novel.
Bookies William Hill and Ladbrokes have Brown's bestseller as the favourite for Christmas number one.
"Dan Brown is the obvious favourite, but by Christmas week most of those desperate to read the book might already have bought it," says William Hill spokesman Graham Sharpe.
And the next few days will see the release of some other contenders for the Christmas crown: Robert Harris's Roman thriller Lustrum, and Eoin Colfer's sixth part of the Hitchhiker's Guide to the Galaxy trilogy, And Another Thing...