E.L. James, writer of "50 Shades of Grey" has topped the Forbes' list of top-earning authors.  She made an estimated $95 million between June 2012 and June 2013.

Forbes accredits her wealth to the fact that she sold more copies faster than any other author in history, which is more than 70 million in the first eight months that they were on sale in the U.S.

Another key factor in her book success was the e-book format, "giving readers an easy way to purchase the sex filled sequels-and a discreet way to read them in public," according to Forbes.

"50 Shades of Grey" originated as fan fiction from Stephenie Meyer's "Twilight," and resulted in two more installments for E.L. James' kinky saga.  The three books alone aren't the only things that have led to her weath.  E.L. James, a.k.a. Erika Leonard, got $5 million for the film adaptation directed by Sam Taylor-Johnson that is expected to hit theatres in August 2014.

The triology is all that the author has written so far, but she is currently working on her next novel, which she cited as a reason to decline an interview with Forbes.

Author James Patterson came in second on the list, with a total estimated $91 million in earnings due to the success of his "Maximum Ride" and "Witch & Wizard" series.

Coming in third is Suzanne Collins with her "Hunger Games" triology, which brought her $55 million.  

Even though J.K. Rowling's big "Harry Potter" success is behind her, she made the list earning $13 million due to "The Casual Vacancy," as well as her surprise crime thriller The Cuckoo's Calling, which she wrote under the pseudonym Robert Galbraith.

It seems the trick is writing a young adult novel that is enjoyed by others, as well.

"Writing thrillers or romances for adults is good; even better is writing fantasy fiction for young adults that spills over into the adult market. The biggest franchises of the past decade have employed this formula," according to Forbes.