You said if one book enters public domain then every book effectively enters public domain from a plausible deniability angle of using the one relevant book. But that makes no sense at all. Because anyone can write a book in the style of Dan Brown without infringing on his IP. You don’t need Starry Night to teach a model to make works like Starry Night. You just need a work like Starry Night. And if you want to argue that the machine can learn style better than humans for text, then how is this ever going to hold up in court as “too similar to the style”?