The following link is to an article on the books prohibited in Texas prisons, specifically ten books on photography. I am guessing that the books contain images of nudity, violence or other possibly contentious subjects.
The scary thing is that I have some of these... maybe I should avoid Texas - despite being a law-abiding individual you never know whose toes you stand on in a foreign place.
https://www.lightstalking.com/ten-photography-books-cannot-read-texas-prisons/