If we’re talking about a public library, they should find the form to reconsider having the book in the library. They typically ask why you think it should be removed, other materials that would be more appropriate, etc.

In the public libraries I know, that goes to their admin department to be re-evaluated. In mine, it’s done by the director and head librarian. It’s not a majority vote by all the librarians, and the librarian who purchased it doesn’t have the final say. All public libraries have a reconsideration policy/collection guidelines. If they review it and find that the book violates those, they’ll get rid of it.

There are ways to appeal their decision as well.