The real question is which books trigger a ping to the FBI and why are those books in your average library? Wouldn't it be clever if the FBI placed those books in libraries just to see who got them out? Now that's a conspiracy theory.
While I understand the issue at hand, I have to say that this is just dumb.
Some of them seem juvenile, but the fact that your reading habits can be monitored without court proceedings is something that every library user should be aware of.
I never would have assumed they couldn't. By a snooping librarian, even if not by the FBI.
I don't think it's likely that a librarian would bother to look through my very boring records, but it's certainly no less likely than the prospect of an FBI agent doing so.
I don't know how many librarians you know, but the ones I know zealously guard the privacy of their patrons. They take that custodial duty extremely seriously. Librarians as a group are some of the staunchest civil rights advocates you will find anywhere.
To each his own, I suppose. I really do not go to the library much, but it'd be a bit sad if they had to confiscate my "How to Do Magic" reading list.