I just finished reading an amazing book about the experience of being a correctional officer at Sing Sing Prison in New York. Newjack is by Ted Conover, who is a journalist and was interested in writing about the officer training academy. When his request was rejected, he instead applied to become an officer, went through the training, and worked as a CO for a year.
It's a fabulous book and really well-written, and sheds some light on what that job really means. Plus there's some really interesting prison history in there as well (interesting to me, anyway, but maybe I'm just the world's biggest nerd). Here's a link to the site with reviews, if you're interested.