part of librarianship is knowing how to evaluate various books to determine if they're worth acquiring for the collection. So, you'd look at book reviews by experts, ask the professor that teaches that subject if there's anything they'd suggest. You research the author, find out if they're involved in any scandals w.r.t. their research, if they have undisclosed conflicts of interest, what have you.

Yes, that sounds trivial, but there's a lot of things that go into it. Librarianship is mostly knowing how to find, store, and make available information.