I recently read a book about experiences in the UK prison system: 'A Bit of a Stretch: The Diaries of a Prisoner' by Chris Atkins (there is an associated podcast, which is also excellent). It is a fascinating, but rather depressing read about his experiences being incarcerated for tax fraud and how broken the UK prison system is. It is no wonder the re-offending rates are so high.

I'm guessing much of the US system (where I understand a lot more for-profit private companies are involved) is at least as broken.