Prisoners would write asking for subjects, not by title since that was super unlikely. Often we would mail a mix of magazines and books.
Every jail has different rules. Each package would get custom consideration for which jail it was going to.
Sometimes stuff would just get confiscated for no reason.
Some of the letters were sad to read. The appreciation and expression of thanks for some random book previously sent.
The date it was read by a volunteer and responded to would be sometimes several months from the date it was written.
It did spur my interest in criminal justice system to some extent. But mostly I took away how sad the conditions were on the inside. As I took for granted my ability to choose and read whatever I liked, whenever I liked.