The Tales of Beedle the Bard by J. K. Rowling
Really enjoyed these short stories. The notes by Professor Dumbledore added a lot of depth to the stories and also mentioned a few characters from the original 7 books (which made me happy inside!).
My favorite story was The Tale of the Three Brothers, because of the tie-in to the 7th book but my second favorite was The Fountain it Fair Fortune.
Let me know which tales you enjoyed in the comments section below.