Unless they have alternative access to paper books, I don’t see how this does not violate their 1A right to books.
There’s a First Amendment right to books in prison? (Genuine question.)
I mean they have the right to read books and other materials[1, 2] (whether the prison is required to furnish them is a different question). But generally, I believe yes, prisoners have a limited right to the 1A in prison. There are some restrictions for security purposes as well as they lose some rights (like right to vote) if they are felons.
[1]https://ncac.org/news/books-behind-bars-the-right-to-read-in...
[2]https://jailhouselaw.org/your-first-amendment-right-to-freed...