Books... Hmm...
Maybe you should read some books that will help you ER properly. Or maybe some philosophical books to really take your mind out of your surroundings.
What kinds of things are you inherently interested in? That is most always the best starting point for picking diversions and amusements.
I've looked up stats for prison-rape, but they are unreliable (as it's not reported, the guards ignore the complaint, it's considered consensual, etc, etc). Also the impression I get is that jail is safer than prison. Also prison rape is apparently only a big thing in the good ol USA.
What I've read about jail/prison is keep to yourself, don't bother anyone, and never accept gifts or favors from anyone. A common trick is for a prisoner to leave a piece of candy in your cell, and if you eat it he accuses you of stealing his candy, and as payback you 'owe' him. That's so retarded. When it's only under the threat of violence, why have the pretense of owing somebody at all? So yeah - don't accept gifts.