The Celestine Prophecy is a good book to have under your belt. The philosophy behind it is interesting, though it was a bit over-hyped when it first came out. It almost seemed as though it was going to become its own religion. Regardless, it's an intriguing read and creates good discussion with others who have read it.
I'd also have to say Animal Farm, as well. The Holy Bible of novels, for me personally. I learned that society is always adjusting itself. Not every situation is perfect, nor can one expect perfection. However, I also learned that people have morals by which they hold themselves. Any leader who pushes his morals upon a group does not deserve power. It taught me to appreciate who I am, what I believe, and how I think.