Nietzsche's On the Geneology of Morality. It's about the evolution of morality, starting with the idea of how the idea of "good" or "bad" likely came to be in the first place.
Michael Foucault's Discipline and Punish. It's about the prison system and death penalty, and how it's evolved since the middle ages.
If you want a fun way to learn about various philosophers, I give you The Simpsons and Philosophy: The D'oh of Homer. I read it several years ago, but I remember it being intelligent and interesting. They basically take apart each character from a particular philosopher's point of view. For example: They discover, through a study of Aristotle's virtues, why we love Homer even though he never seems to do the right thing.
I read the simpsons and philosophy as a kid and found it pretty accessible:
http://smile.amazon.com/The-Simpsons-Philosophy-Popular-Culture/dp/0812694333?sa-no-redirect=1