What we know so far: A market built for libraries and booksellers is now feeding AI training, as companies seek large volumes of printed books that predate the generative AI boom. ISBNdb, which says it maintains the world's largest book database, now helps AI companies source physical books in bulk. "The world's best AI training data is sitting on a shelf," the company says on its website. "Print books from the pre-LLM era are structurally guaranteed to be free of this contamination," the company says. "'AI company destroys two million books' is not a headline that generates sympathy."