CANNES, France (AFP) -- Hollywood has always adapted the classics but film and television's voracious appetite for new material now has film-makers raiding the bookshelves like never before.

Six of the movies in the running for the Cannes film festival's Palme d'Or top prize -- which will be awarded Sunday -- are taken from books.

Sofia Coppola drew from Thomas Cullinan's classic Southern Gothic novel for "The Beguiled" starring Colin Farrell as a handsome Union officer who stokes sexual tension and jealousy inside a girl's school during the American Civil War.

And Francois Ozon turned up the temperature of Joyce Carol Oates' sexual psycho drama "Double Delight" to almost unbearable levels for his steamy "Amant double".

The thirst for gripping new yarns has been fuelled by the boom in high-quality television series, meaning there are only so many good scripts going round, experts argue.

Which is why "cinema, like TV, is on the look out for really good stories", said Judith Becqueriaux, of the French publishing house Denoel.

"And a good book gives you a story which has already won over the public," she added.

"There is more and more demand" for books to adapt, insisted Nathalie Piaskowski of the main French publishers' body, with cinema adaptations rising by a fifth according to the latest available figures.

Such is the demand that film-makers are not even waiting for books to be published before snapping up the rights.

More than 130 international producers took part in a special book rights market at Cannes this week, with publishers pitching them some of their new releases and soon-to-published novels.

"A book adaptation gives a certain guarantee of success and helps the film get made," Piaskowski argued.

Cannes is only one of a growing number of festivals were publishers are bringing books to be optioned for the screen. The Berlin festival has its own showcase called "Books at the Berlinale" in a link up with the world's biggest book market, the Frankfurt Book Fair.

Similar organised "pitching sessions" are now also taking place in Los Angeles and Shanghai.

Some of the biggest deals in Cannes this year were for children's books, with the movie franchise of the Moomins, the Finnish storybook characters, sold to China.

This comes as "Valerian and the City of a Thousand Planets" -- the most expensive European film ever made at $190 million -- is about to hit the screens in July.

The massive project from Luc Besson, of "The Fifth Element" fame, is based on a French comic book.

"For the last decade or so more and more film-makers are drawing from graphic novels because it's a super base and the stories are already well developed," said Alexis Ducord, whose comic animated film about a family of zombies, "Zombillenium", was shown at Cannes.

"In a 12-month period, eight films drawn from books in our back catalogue have either been released or are about to be released," said Helene de Saint Vincent, who handles the rights for three graphic novel houses.

But most directors are not interested in directing a book's narrative "straight", according to Nathalie Carpentier, whose company CAL deals with a number of international publishing houses.

Instead they are looking for a "story which they can play with like a Playmobil toy and that will have enough action and emotion for the director to show that their film isn't simply bringing the book to the screen".

But having a book optioned for a film is not quite the financial boon that many people believe.

Average rights now sell for around 45,000 euros ($50,000), with the biggest deals reaching 200,000 euros -- with only a fraction of that going to the authors.