Why Do You Read Books from the "Dark Side" of Humanity?

I enjoy reading war stories (I don't know why!), and City of Thieves by David Benoit had a twist: Two unlikely prisoners hunting for an elusive item that will save their lives. Throughout the story, you get to know each of the characters pretty well as they spend their time engaged in a type of scavenger hunt in Leningrad during WWII. In this well-written book, the author writes with wisdom, dark descriptions, and some humor. I appreciated the development of character (one likable, and one not so much!), and I look forward to reading other books by this author. While parts of the story were brutal, the overall reading was worth it. Well, I suppose I just answered the question . . . I read books on a variety of dark topics if I care about the characters, I learn something in the process, and there is some redeeming quality to it!  Why do you read these types of books (if you do!)?