God bless your family.
As for books, it has to do with whether your wife wants books that will help her escape a bit from her surroundings, or better understand them. Other posters are assuming it is the first, and I suppose that most people would feel that way. But everyone is different.
I loved
Orange Is the New Black: My Year in a Women's Prison:
http://www.amazon.com/Orange-Is-New-.../dp/0385523394
Author Piper Kerman mentions in there books she read to prepare (she had very long advance notice of incarceration). I can't recall what they were, but some are probably here:
http://www.amazon.com/s/ref=nb_sb_no...men%27s+prison
Just to open it up to categories other than fiction, and non-fiction about prisons, this gives ideas that maybe you could run by your wife:
http://chicagobwp.org/how-to-help/donations/