The Fool of the World and the Flying Ship by Arthur Ransome
The fool of the world, despised and rejected by his own family for being stupid, wins the hand of the Princess against all odds. This is a classic tale of the good man and underdog winning over the smart guys.
Beautifully written and illustrated, this is one of the most magical folk tales retold with wit and charm; one of the best fantasy books around, and a Caldecott Medal winner.