James says the idea for the Fifty Shades trilogy began as a response to the vampire novel series Twilight. In late 2008 James saw the movie Twilight, and then became intensely absorbed with the novels that the movie was based on. She read the novels several times over in a period of a few days, and then, for the first time in her life, sat down to write a book: basically a sequel to the Twilight novels. Between January and August 2009 she wrote two such books in quick succession. She says she then discovered the phenomenon of fan fiction, and this inspired her to publish her novels as Kindle books under the pen name "Snowqueens Icedragon". Beginning in August 2009 she then began to write the Fifty Shades books.
The combined novels have sold over 125 million copies worldwide, over 35 million copies in the United States and set the record in the United Kingdom as the fastest selling paperback of all time. In 2012, Time magazine named her one of "The World's 100 Most Influential People." The novels were subsequently adapted into the films Fifty Shades of Grey, Fifty Shades Darker, and Fifty Shades Freed.
James has spoken of her shock at the success of the books. "The explosion of interest has taken me completely by surprise" she said. James has described the Fifty Shades trilogy as "my midlife crisis, writ large. All my fantasies in there, and that's it." She did not start to write until January 2009, as she revealed while still active on FanFiction.Net: "I started writing in January 2009 after I finished the Twilight saga, and I haven't stopped since. I discovered Fan Fiction in August 2009. Since then I have written my two fics and plan on doing at least one more. After that... who knows?" In August 2013, sales of the trilogy saw James top the Forbes' list of the highest-earning authors with earnings of $95m which included $5m for the film rights to Fifty Shades of Grey. On 1 June 2015 James announced the upcoming release of Grey: Fifty Shades of Grey as Told by Christian, which was released into stores on 18 June 2015. Darker: Fifty Shades Darker as Told by Christian was released November 28, 2017.
James was one of the British celebrities, including Tom Hiddleston, Benedict Cumberbatch and Rachel Riley, to design and sign her own card for the UK children's charity Thomas Coram Foundation for Children. The campaign was launched by crafting company Stampin’ Up! UK and the cards were auctioned on eBay during May 2014.