‘They’re likely to get squeezed’: AI slop books are flooding online marketplaces—and it’s coming at the expense of paychecks for human authors

In March, the book publisher Hachette yanked the horror title “Shy Girl” from its scheduled U.S. release after hefty allegations that the novel’s author Mia Ballard used AI to write the book.

While Ballard denied using AI for the novel, Hachette pulled the book from its website, Amazon , and U.K. shelves, but the incident became a moment of reckoning for the book industry: What should booksellers do about AI-generated books, particularly as they proliferate across marketplaces? Today, the urgency to answer that question is growing.

Recent research shows the magnitude of AI-generated books in online marketplaces presents a problem for human authors, and has the potential to change the landscape of bookselling more broadly.

An Originality.AI report published last month found that of more than 2,000 books on religion published on Amazon over the last 12 months, 1,272 titles, or 63%, were flagged as being likely written by large language models.

A Stony Brook University-led study found that of 14,419 self-published genre-fiction books sold on Amazon between 2023 and 2026 and run through AI-detection software Pangram, 2,880 (about 20%) had “substantial” AI text, meaning more than 25% of the book’s prose was flagged as AI-generated.

Additionally, 2,168 had more than 50% of its prose AI-generated.

Nearly 1,000 novels were more than 90% AI-generated.

This study, which has yet to be peer-reviewed, found that more AI books came at the expense of revenue.

Over the period of three years, the number of books with observed sales in a quarter increased 19.2-fold, but quarterly revenue increased only 8.9-fold, indicating decreased revenue per book sold.

The effect, according to the researchers, was that the sheer magnitude of books flooding the marketplace made it less likely that an Amazon customer would select a given book written by a human, leading to fewer sales of any given title, and less money in the pockets of human authors.

“The crowding-out effect generated by these books—most of which are low quality, but some of which are still good enough that they lead to higher ranks—due to this increased competition, they’re likely to get squeezed, and their revenues are reduced,” Paramveer Dhillon, an associate professor of information at the University of Michigan and the study’s coauthor, told Fortune .

Amazon requires self-published authors to disclose if they’ve used AI to generate texts, and limits the number of titles they can upload to the site to three per day.

“We are committed to a bookstore that readers love and publishers and authors trust, with multiple safeguards we continuously strengthen to protect their experience,” an Amazon spokesperson told Fortune in a statement.