Film rights to the erotic bestseller Fifty Shades of Grey have been sold to Universal Pictures after a major bidding war was waged over the weekend.

The book, part of a trilogy written by British author E.L. James, has been an overnight literary success, selling an estimated 10,000 copies per day. The bondage erotica story has been dubbed "mommy porn" by some.

"The Fifty Shades Trilogy is a one-of-a-kind series of stories and we're thrilled to be collaborating with E.L. James to bring them to the big screen," Universal Chairman Adam Fogelson and co-chairman Donna Langley said in a statement. "Like so many readers all over the globe, we've fallen in love with Fifty Shades of Grey."

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Erotic novel Fifty Shades of Grey has seen a surge in popularity. (The Writer's Coffee Shop)

Inspired by the popularity of the Twilight series, James initially published the book independently online,  before her work was picked up by a small Australian publishing house. It was then bought by a major U.S. publisher — it is now on the New York Times bestseller list.

The trilogy is rounded out by Fifty Shades Darker and Fifty Shades Freed.

Popularity spread by word of mouth

The story revolves around graduate student Anastasia Steele, who meets Christian Grey, an eligible and wealthy bachelor whose sexual desires lean towards masochism and bondage. Its popularity with women in their 30s and 40s has led the book to be found in many suburban book clubs.

Penny-Ann Lupton, an avid fan of the book from Brantford, Ont., told CBC News that she felt a distinct connection to the characters and was quick to spread the word.

"All my neighbours have read it now, they all love it. And their husbands love me," she said. "They got very 'friendly' after they read it!"

Lyss Stern, whose website Divalysscious Moms caters to expectant and new moms, promoted the book online and noticed its popularity grow.

"I think it's interesting that it is capturing this demographic," she told CBC News. "I think women when we have children it's all about our children and careers. We forget to remember that fantasy and I think that's what's resonating."

E-books perfect medium for erotica

The renewed interest in erotica has led publisher HarperCollins to launch a new e-book imprint to cater to growing demand. The offshoot, known as Mischief, launched on March 27 with 13 titles including A Study in Shame by Lucy Salisbury, Kinky by Justine Elyot and Red Grow the Roses, a vampire erotic novel by Janine Ashbless.

A HarperCollins spokesperson said erotic novels lend themselves well to e-books because fans of the genre can read them anywhere without anyone being the wiser.

"The world of erotic fiction is proving so popular on the Kindle," he said. "It has to do with the anonymity and no one knows that you are reading it. We've now seen a resurgence in the genre."

The publisher has signed deals with 60 authors and plans to release a large number of titles over the next year.