Books to Prisoners, an organization run by the bookstore Left Bank Books, has been accumulating lists of banned books in various prisons for years. You can see the information here:
http://www.bookstoprisoners.net/banned-book-lists/.
In my state, for example, everything from
How to Draw Birds to
Fifty Shades of Gray are banned. Sure, there is also a ton of stuff on the list that is pornography or clearly violent, etc. But I do know that the list is not static. A warden can see a book come in and decide only after the prisoner has paid for it that it is going on the banned list. It is confiscated and the prisoner doesn't get his book or his money back.