It is an excellent book that underscores some of human nature's uglier tendencies and also the better ones. At the moment my DH is reading The Adventure's of Huckelberry Finn to me & our 2 kids, ages 11 & 12. We're using it as an opportunity to discuss American History in a way that simply isn't possible from a textbook perspective. My kids totally 'get' the objectification inherent in the character's speech & behavior.
The classics are classics for a reason and mostly have value in their ability to take a verbal snapshot of the sensibilities of a particular point in time. I know there is a great deal of debate over some of these books but, in my opinion, if they are handled delicately, as they should be, they can be invaluable in teaching deep morality. "The Crucible" is another one that warns against getting behind a crowd with blind trust. It talks about religion but could easily apply to any mass movement because as a group, people are easily manipulated. It also touches on how individuals can use group mood to further individual agendas... a very cautionary story IMHO.
I think I read "To Kill a Mockingbird" when I was about 13, maybe it's a good choice for our next family selection. Thanks for reminding me about it.