The club of the world's top-selling authors is an exclusive one, with only a few established paths to entry. Many of its members have been in it for decades, like Danielle Steel and Stephen King, who were both born in 1947 and published their first novels, "Going Home" and "Carrie," in 1973. This year, Steel is No. 5 on the list and King is No. 10.

If you're not writing in a genre with mass commercial appeal, you can pretty much forget about making the list. But even if you are, and your books are best sellers, that's still not a guaranteed in.

To really be assured of the millions, you'll want to crank out the titles at a furious pace of five or more a year. That's the not-so-secret secret of mega-authors like James Patterson (No. 2 on our list with $91 million in earnings between June 2012 and June 2013) and Nora Roberts (No. 8, $23 million).

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, most recently Suzanne Collins‘ "The Hunger Games" trilogy. Collins' earnings of $55 million — good for No. 3 on our list — also showed the power of a hit film adaptation, which can launch a book from the earthly best-seller list into the stratosphere.

Then there's "Fifty Shades of Grey."

E.L. James — known to her friends and family as Erika Leonard — didn't follow any of the rules for getting to the top, but she's there all the same, debuting on the 2013 top-earning authors list with an estimated $95 million in earnings. (FORBES bases its estimates on sales data, published figures and information from industry sources between June 2012 and June 2013.)

There's no film version of any of the "Fifty Shades" books, although she did pocket $5 million for an adaptation that's expected in theaters in August 2014. While the plot of the novels was inspired by "Twilight" — indeed, they originated as fan fiction based on Stephenie Meyer's vampire characters — they're certainly not crossover material, unless you think kinky sex belongs in a children's book. And James is no one-woman fiction factory: The three "Fifty Shades" installments are all she's written so far, although she is at work on her next novel (and cited her writing when declining an interview request).

So how did James, a former television executive who lives in the U.K., do it? Simply by selling more copies faster than any other author in history — more than 70 million in the first eight months they were on sale in the U.S.

The following are the top 10 top-earning authors in the world.

 Stephen King: US$20 million

Less prolific than some of the other authors on this list, King has his up and down years, but he's enjoying yet another moment of cultural ubiquity, with CBS's "Under the Dome" one of the biggest new hits on network television and a long-awaited follow-up to "The Shining" coming to bookstores. King also has two sons who are successful novelists.