Another guy I met once who is still in prison said that he spent 6 months in solitary. He spent his entire time strengthening his fingers so he could climb brick walls with just his fingertips. An odd thing to do but when you have nothing but your body in a cell you can only spend time getting fit or wasting away.
Most prisons have outreach programs. You can go and teach someone to read (or program). It is a very interesting experience and you may even get someone interested in a topic enough to save them from the system (or themselves).
I'm confident I could do a month alone in a reasonable room with just books and paper and enjoy it (the only cost being the forgone opportunity to do other stuff, but it would be overall enjoyable) -- catching up on a lot of fiction, history/biography, and tech reading. 6-12 months with a computer, preloaded with development tools and books, but no live Internet access, would be fine too. I really don't understand the people who think a 3-5 year mars mission with only a few other people would be that psychologically difficult.
I don't know about you but I think I'd struggle to survive more than a day or two.
(I'm 99.9% certain you could get a bible, if nothing else -- while I'm an atheist, it would be interesting reading, if only to understand cultural references, and is quite long. Law books would be great, and there are legal arguments ensuring access to those, too.)
But not even the US prison system should want to limit prisoner's intellectual development! To help prisoners grow will make a subset of them productive members of society instead of parasites. Win-win.
Edit: I'm a European, but not dogmatic. My native Sweden should imho use harsher sentencing in some areas. But this was just ridiculously contra productive.
You do realize that if you make prison overly "humane", it eliminates prison as a form of deterrence.
And conversely, there is plenty of evidence that severity of punishment does not have a significant impact on crime rates.
The simple "heavier punishment -> less crime" appeals only to simplistic logic, but in general is not observed in reality, either in the US or abroad.
The odd thing about many people in the "deterrence" crowd is that so many don't seem to actually be concerned about lowering crime rates, and are concerned moreso with exacting their pound of flesh for the injustice committed by criminals.
Making prison "suck less" might even give inmates a shot at a life after they are released. But given that you see prison "suckage" as a feature (especially given the generally accepted ideas of what goes on in prison), I can only conclude that you've ruled out any possibility of yourself ever ending up there, and thus don't really care.