How much money do a inmate need for their books?

If you ask an inmate (as you are now), the more the merrier :)... but you as a person on the outside trying to take care of your own expenses you should budget what you can afford to send. If money is no object, you might consider $75/wk for commissary and phone. In the federal system, they can only spend $69/month on phone and $315 on commissary + whatever money the emails are. It can become quite expensive so be careful and protect yourself from overdoing it.