The Odious Ogre — Norton Juster

This is the story of a really rotten Ogre who is extraordinarily large, exceedingly ugly, unusually angry, constantly hungry, and absolutely merciless. He terrorizes the entire countryside and all the surrounding towns, wreaking havoc, sowing confusion, and dining happily on the hapless citizens. Nothing can stop him. But then he takes a wrong turn and encounters a kind and friendly young lady who does her best to help him--with a surprising result.