Books Through Bars is an all-volunteer nonprofit based in PA that distributes free books and educational materials to incarcerated people in PA, NJ, NY, MD, DE, VA and WV. Consider donating books or getting involved in their other prisoner support programs!
From their website:
We also offer programs that educate and engage the general public to think critically about issues of imprisonment. Each week, we receive hundreds of letters from prisoners requesting books. Each year we send over 8,000 book packages. We welcome all who wish to learn and help.