I think this misses the point. The issue of scale isn't on the ingest side, it's on the output side. Once you train an LLM on a book (however long that takes), then the LLM can be the interface to that book for an unlimited number of users. That scales very differently to, say, a person reading a book and writing something influenced by it.
In the case of the LLM, it's a complete interface to the contents of the book. It lets you "talk to the book". If that exists, why would anyone buy the book? If I could ask ChatGPT to "summarize the new book by XYZ", then spend an hour or two asking the questions _I_ have about the book from it, then buying the book would be a net negative.
If we don't solve attribution (like BMI solved for music), then the financial upside of publishing might be majority-captured by whoever trains LLMs on the copyrighted material.