HarperCollins said in a statement to 404 Media that its deal will include “select nonfiction backlist titles” and that authors will have to opt into the training program.

One author, Daniel Kibblesmith, posted screenshots a few days ago showing that he was offered $2,500 per book for a three-year AI licensing contract. Asked what would be an offer he’d consider taking, Kibblesmith said in a post on Tuesday, “I’d probably do it for a billion dollars. I’d do it for an amount of money that wouldn’t require me to work anymore, since that’s the end goal of this technology,”

Not much else is known about the model HarperCollins’ content will train, but a source tells Bloomberg that Microsoft doesn’t intend to generate AI-written books with the material. Microsoft declined to comment.

News Corp, the parent company of HarperCollins, struck a deal with OpenAI earlier this year, allowing the AI giant to train its models on New Corp’s digital outlets, including The Wall Street Journal, the New York Post, The Daily Telegraph, and more.