The Tale of Despereaux: Being the Story of a Mouse, a Princess, Some Soup, and a Spool of Thread by Kate DiCamilio
This book is utterly charming. How can you not like a tale of bravery about: a mouse with huge ears, a rat who wears a spoon on his head, and a kingdom in which soup has been outlawed?
It's not exactly light-hearted all the time, though. There is also: a girl who has lost her hearing due to being boxed in the ears; a man who sells his daughter for a tablecloth and a dungeon full of blood, rats & a "terrible, foul, extremely insulting smell."
If that doesn't make you want to read it, then you are a better woman than I. It won the Newberry Award, as well.