The author of the Fifty Shades franchise Erika Mitchell, better known by her pen name E.L. James, has said that she remains confounded by the success of the books and films.

The British author wrote the erotic romance trilogy “Fifty Shades of Grey,” “Fifty Shades Darker” and “Fifty Shades Freed,” which together sold some 165 million copies, and companion novels “Grey: Fifty Shades of Grey as Told by Christian,” “Darker: Fifty Shades Darker as Told by Christian” and “Freed: Fifty Shades Freed as Told by Christian.”

The trilogy was also made into films, which together grossed more than $1 billion, on which Mitchell served as a producer.

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“The success of Fifty Shades still confounds me. I was like a rabbit in the headlights. I didn’t expect such a furore and didn’t deal with it well. I couldn’t sleep and was anxious, especially around the time of the movies,” Mitchell wrote in a column in the U.K.’s Sunday Times.

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“All I’d done was sit down and write something I’d have wanted to read, an erotic and fun romance. At the heart of my books are the characters and their relationship, which I really care about. End to end bonking would be pretty boring,” Mitchell added. “I have imposter syndrome and knowing I’ve sold 165 million books doesn’t make it easier. I find it depressing that I can’t shift the self-doubt so I’m in therapy now.”

The film series star Dakota Johnson has spoken about battling Mitchell for creative control.

There might be another movie in the works. “We’re not taught how to be happy, and women in particular get bogged down with the minutiae of life. I’ve just turned 60 and am trying to focus on enjoying my life more, to appreciate time with family and friends,” Mitchell wrote. “I’d also like to make a movie that I really love.”

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