Yeah, I feel like this article's outrage at the inability of prisoners to get used books is unwarranted. What actually deserves this level of outrage is the violence encountered by many in prison as you mentioned.
Imagine going to prison for a small-time felony, and having to deal with widespread rape[1], gangs[2], and drugs[3]. Many of the people are in prison did seriously bad things, and should be allowed out any time soon. But, the eighth amendment also says people should not be subjected to cruel and unusual punishment [4]. But perhaps I'm just soft like Tom DuBois from The Boondoks.