Restoration of Faith by Jim Butcher
Blurb from Goodreads:
A short story of the Dresden Files that takes place before Storm Front.
A cute little tale that introduces a great many characters and a tiny glimpse into the life of Harry Dresden. This glimpse bringing a yearning to read more and find out what else lives in the dark and the magic that can defeat it. It was nice to learn more of the past of the characters and to feel more involved with them.