Stu, if you want to read a good philosophy survey that won't grossly underestimate your intelligence, try The Story of Philosophy by Will Durant, who, I might add, possessed one of the great minds of the 20th century. I read it when I was about your age.

When you're done with that, you can try tackling his The Story of Civilization -- all eleven volumes of it. Alas, I have yet to work up the courage to do so, myself.