British writer E. L. James attends a book signing at Barnes & Noble. Over 500 fans turned out to meet the controversial author who's novel '50 Shades of Grey' has been dubbed 'mommy porn' and hit the headlines after being banned from a Florida library. (Michael Carpenter/ WENN.com)

British author E.L. James' saucy and sensational Fifty Shades Of Grey has passed The Hunger Games as the bestselling book of 2012, accounting for 25% of adult fiction sales in America.

The erotic book has hit 10 million in sales, six weeks after hitting stores.

The three books in James' series also top The New York Times, USA Today and Publisher's Weekly best-seller lists.

Universal and Focus Features have won a multimillion-dollar bidding war for the movie rights to the book.

Anthony Chirico, president of Knopf Doubleday Publishing Group, says, "This is an astonishing number. The sales velocity for Fifty Shades of Grey is unprecedented, with reader demand still growing. BookScan data indicates that the trilogy has captured 25% of the adult fiction market in recent weeks. As we head into the heart of the summer reading season, sales are likely to continue exceeding even our most optimistic forecasts."