You may want to check out this site:
Women's Prison Books Project. This is a site devoted to collecting books for women in prison, but some of their advice about what does/doesn't raise issues with prison administration might be useful.
One suggestion that I remember from their page: poetry books or other books with lots of white space might be valued. Apparently blank books are sometimes disallowed because they want the prisoners to spend money at the canteen, so books that make good writing material but don't look like it can be useful to inmates.
Disclaimer: I have zero affiliation with this organization and know little about them beyond seeing a mention online and being curious enough for a little followup.