'Fifty Shades of Grey' author: Books were my 'midlife crisis'

Breakout author E.L. James - the woman behind that deliciously racy novel “Fifty Shades of Grey” - admits that the motivation behind her steamy storylines was actually her own “midlife crisis.”

"It's all my fantasies in one thing," the British writer said of her publishing hit and its two sequels in a recent interview with ABC’s “20/20."

“It's a contemporary, romantic fiction, with quite a lot of sex in it," James, who is married with two teenage sons, said of the trilogy's popularity. "I think it's the love story... I hope it's because of the love story."

"Fifty Shades of Grey,” as well as "Fifty Shades Darker" and "Fifty Shades of Freedom," tells the story of Christian Grey, a charming billionaire/S&M fetishist.

'Fifty Shades of Grey' shines light on erotic fan fiction

So far fans have bought into Grey's highly sexualized lifestyle in a very big way: within a year of the books' independent release online, more than a quarter of a million of them have been sold.

Their runaway popularity led to James – who uses a pen name but whose real name is Erika - scoring a book deal with Vintage and a movie deal with Universal reportedly worth $5 million.

Ironically, James' initial marketing plan didn't cost anywhere near that: the first-time author and former television executive says she started by posting her writing - which would later become the "Grey" series - on a fan site for the "Twilight" books.