Candide by Voltaire
Candide lived in the magnificent castle of Thunder-ten-tronckh with the Baron and his family. Candide was rumored to be the illegitimate son of the Baron's sister. The tutor to the children, Pangloss, teaches the philosophy "all is for the best in this best of all possible worlds."
The Baron's daughter, Cunégonde, sees Pangloss in an intimate moment with the servant Pacquette. This leads her to tempt the naive Candide. Caught by the Baron, Candide is expelled from the castle.
As Candide travels the world and sees one evil after another, he begins to question the optimistic philosophy taught by Pangloss. During one voyage he meets Martin. Martins philosophy is pessimism that sees evil as the dominate force of the world.
Voltaire's satire pokes at philosophy, religion and government. It's a small book, but it's action-packed and very witty. It's a thought provoking book I'd recommend to everyone.