By recommendation I read Sophie's World by Jostein Gaarder. It is a novel about the history of philosophy, written in such a way the the concepts from the pre-Socratics through Kant and up to Sartre could be grasped by a juvenile. Spoilers past the jump.
This book is sort of a novel, but moreso it uses a storyline to paste together summaries of different philosophies. Sophie starts getting these strange correspondence course philosophy lessons and gets these stranger pieces of flotsam from some girl named Hilde. To cut to the chase, Sophie and her teacher figure out that they are just characters in a story written by Hilde's father for Hilde. They strain under this yoke and attempt to escape from the somewhat capricious behavior of the creator of Sophie's World. Jostein Gaarder winks at us when Alberto [the philosophy teacher] says that Hilde's father might be a part of a story being written by someone else. Sophie even ends up buying a copy of Sophie's World in a bookstore. Levels within levels.
Sophie and Alberto manage to escape from under tha major's thumb and enter a world where spirit is stronger than matter, Winnie-the-Pooh and other fictional characters inhabit this world, but it is just as real as real is. It is somewhat creepy to think that we are gods and that the stories we tell go on living after we tell them. Think would make for a more responsible storyteller, I think. It is a different tack on Tolkien's idea of subcreation and mythopoeia.
The philosophical portions are balanced, not too long-winded, and gives the best cuts of meat in terms of the specific philosophers ideas. It doesn't try its own Meaning of Life attempt, instead it says that the same questions that philosophy has asked for thousands of years must be answered by each person in every generation.
"He who cannot draw on three thousand years is living from hand to mouth."
Johann von Goethe.