Mr. Tager said he had grown increasingly concerned over restrictions on books about civil rights or prison conditions — issues that people in prison might confront daily. Among the examples in the report is a move by the Arizona Department of Corrections to ban the book “Chokehold: Policing Black Men,” which is about the subjugation of black men in the American criminal justice system.

The Arizona Department of Corrections previously said in March that “Chokehold” was unauthorized because of concerns it might be “detrimental to the safe, secure and orderly operation of the facility.”

The department reversed itself in June after the American Civil Liberties Union threatened a First Amendment lawsuit, The Arizona Republic reported.

Another type of restriction targets broad categories of books, regardless of their content.

The report cites an example in New York where, in 2017, the State Department of Corrections and Community Supervision started a pilot program that limited the books that people in prison could receive to those offered by five preapproved vendors.

Books Through Bars, a nonprofit, said that would have limited the books available to “five romance novels, 14 bibles and other religious texts, 24 drawing or coloring books, 21 puzzle books, 11 guitar, chess, and how-to books, one dictionary, and one thesaurus,” according to the PEN report.

Gov. Andrew M. Cuomo suspended that program in 2018. The department said in a statement Thursday that it did not ban books, and that the program to limit the vendors was designed to stem the flow of drugs and other contraband into prisons.

The department said it was currently working to deliver tablets to inmates statewide by mid-October, which would give them access to some e-books, free music and videos.