There was one major difference between the books: The Auction Deal had sex scenes and was being marketed as mainstream romance—the most profitable category in self-publishing. “I was floored,” Nunes said. “I didn’t believe it was true that someone would do that.”

In the world of self-publishing, where anyone can put a document on Amazon and call it a book, many writers are seeing their work being appropriated without their permission. Some books are copied word-for-word while others are tinkered with just enough to make it tough for an automated plagiarism-checker to flag them. (Though the practice is legally considered copyright infringement, the term “plagiarism” is more widely used.) The offending books often stay up for weeks or even months at a time before they’re detected, usually by an astute reader. For the authors, this intrusion goes beyond threatening their livelihood. Writing a novel is a form of creative expression, and having it stolen by someone else, many say, can feel like a personal violation.

Often, the perpetrator’s identity is shrouded in mystery. When Nunes tried to find out more about Mullens, things started to get weird. The anonymous person on the other side of the computer seemed to multiply into an array of fake online identities. Strangers posted Facebook messages attacking Nunes’s character, and hostile one-star reviews began appearing on her Amazon author page. “I felt like I was being attacked,” Nunes said. “When I went on social media, I didn’t know what would be waiting for me.”

The stress took its toll on Nunes. She couldn’t sleep or write and gained 20 pounds. She was faced with the choice of either letting the plagiarism go in the hopes the harassment would stop, or fighting back through the legal system. Finally, Nunes decided to sue for $150,000 in damages, rallying financial support with a GoFundMe page. She alleges that the person behind it all is Tiffanie Rushton, a third-grade teacher who didn’t return attempts to contact her about this article. The case is set to go to trial later this year.

Nunes’s situation is hardly an isolated incident. There are pages on sites like Goodreads dedicated to identifying fake books, including plagiarized novels. Most of the plagiarism is happening to romance novels, which accounts for the largest proportion of ebook sales, but new cases are popping up in other genres as well, from cookbooks to mystery novels. Even public-domain classics like Alice's Adventures in Wonderland and Dracula have been adapted and passed off as original works.

For authors, finding out their book has been plagiarized can be traumatic. This was especially the case for the best-selling author Opal Carew, who learned her serial romance Riding Steele had been plagiarized the same day her sister died from cancer. An hour after her sister passed away, Carew got an email from a friend saying the novelist Laura Harner had changed the genders of the characters in Carew’s work and published it under a different title. Apparently, Harner had done this before, stealing Becky McGraw’s novel My Kind of Trouble, switching genders, and calling it Coming Home Texas. For Carew, the news added surreal stress to her grief. “All my writing friends were sending me condolences about plagiarism, and all I could think about was my sister,” she said.