Not only do books offer prisoners entertainment, but they can also help them prepare for re-entry into society. For example, they can work to get their GED, to improve their vocabulary and language skills, or to prepare for a new career. Prison libraries have pretty strict policies on what they do and don't accept so check out their website before sending your books! Hardback fiction, children's books, true crime stories, or academic journals, for example, are unlikely to be accepted. Here are a few organizations that accept book donations:
— Prison Book Program provides books that offer entertainment and practical information to prisoners. The organization has an extensive guide to the books they accept so check it out before sending anything!
— LGBT Books to Prisoners provides books to queer and trans people who are incarcerated to help them deal with the isolation and marginalization they may experience in prison.
— Women's Prison Book Project provides books to female-identifying people; their website says they are in need of “material on families, children, women’s self-help, women’s health, and legal aid pertaining to women who fight back against their abusers.”