It’s important in the fair use assessment to understand that the training itself is fair use, but the pirating of the books is the issue at hand here, and is what Anthropic “whoopsied” into in acquiring the training data.
Buying used copies of books, scanning them, and training on it is fine.
Rainbows End was prescient in many ways.
It remains deranged.
Everyone has more than a right to freely have read everything is stored in a library.
(Edit: in fact initially I wrote 'is supposed to' in place of 'has more than a right to' - meaning that "knowledge is there, we made it available: you are supposed to access it, with the fullest encouragement").
They're merely doing what anyone is allowed to with the books that they own, loaning them out, because copyright law doesn't prohibit that, so no license is needed.
What is in a library, you can freely read. Find the most appropriate way. You do not need to have bought the book.
¹(Edit: or /may/ not be allowed, see posts below.)
I'd be interested to know if you knew of one with bright line rules delineating what is and isn't allowed.
(I know by practice but not from the letter of the law; to give you details I should do some research and it will take time - if I will manage to I will send you an email, but I doubt I will be able to do it soon. The focus is anyway on western European Countries.)