I think the article buried the lede:

Division of Correction Director Dexter Payne said 50,000 books were available via the tablets. Almost all people housed in ADC facilities have a tablet — only those in “punitive isolation” do not.

The tablets are potentially free, but the content is not. Prisoners have to pay for content, of which the department of corrections collects a healthy percentage. Prisons also charge heavy fees or fines for damage to the tablets that then comes out of any money the inmate has available to them.

This whole restrictions on paper books smells like a way to force inmates to have to pay for what they had for free as books as gifts from family and friends on the outside.

Yeah, who’d want prisoners expanding their minds, improving their critical thinking or preparing to reintegrate into society as useful citizens? /s