There are some general rules to observe when sending books to an inmate in TDCJ:

1) The book or package it arrives in must not contain contraband;
2) The book must not contain information about manufacturing explosives, drugs or weapons;
3) The book must not be written "solely for the purpose of" "achieving the breakdown of prisons" through strikes, riots, or gang activity;
4) The book must not have instructions on how to set up "criminal schemes";
5) The book must not contain "sexually explicit images". (The prison makes "a specific determination … that the publication is detrimental to offenders’ rehabilitation because it would encourage deviant criminal sexual behavior")

When a book arrives at the mailroom, the mail room staff first checks the book against the master list of approved or denied publications. If the book is not on the master list as approved or denied, the mail room officer decides if it contains objectionable content.

Inmates may appeal the decision of a mailroom to deny a book. The publication is then sent to Huntsville for a formal review. If the administration then decide that it is acceptable, the publication is delivered to the inmate; if it is denied, the inmate may choose to have the book destroyed or returned (at the inmate's expense). Most books may only be appealed once.

However, many books have been denied by TDCJ mailroom staff and it is always worth checking on the following list to see if the book you want to send has already been denied (list dates from 2011):
https://reports.zoho.com/ZDBDataSheetView.cc?OBJID=218053000000015004&STANDALONE=true&privatelink=6ff8156ec3e31e2e2160733786c8d97b&ZDB_THEME_NAME=brown