Everyone's suggesting books to get, which is fine, but I had something else in mind:
I have a friend who teaches library science and has worked in libraries. One of the libraries she worked in gets donations of books from people. Sometimes donated books are... not great, but for whatever reason they have to catalogue the book and put it on the shelf. One of the books that came in was a terrible abstinence-only sex-ed book, which she really didn't want the students to find in the sexual health section of the library. So, she looked through the book and found one page with a Bible verse. Since the page had a Bible verse, she could justify putting the book in the "Religion" section -- a section that students were far less likely to look at than the sexual health section. I'm not sure how much power you have over how books are catalogued in your library, but if you have any choice in the matter, I guess that's the sort of strategy you could consider -- trying to make sure the good books are easier to find than the bad ones.