Plenty of things. Apart from the fact that books contain secret truths and knowledge that humankind was never meant to read about, there's also the meat smell and the poisonous gases. Oh. And I got bitten once; I wasn't really paying attention.

Also, librarians. They did kidnap all of the town's children for their treacherous Summer Reading Program, and I'm pretty sure they ate Paolo, so if you're ever looking for a book in Night Vale, for the love of god, do not go to the library.