What-The-Dickens by Gregory Maguire

"Gregory Maguire does for the dark and stormy night what he did for witches in Wicked." — The  New York Times Book Review

A terrible storm is raging, and Dinah is huddled by candlelight with her brother, sister, and cousin Gage, who is telling a very unusual tale. It’s the story of What-the-Dickens, a newly hatched orphan creature who finds he has an attraction to teeth, a crush on a cat named McCavity, and a penchant for getting into trouble. One day he happens upon a feisty girl skibberee working as an Agent of Change — trading coins for teeth — and learns of a dutiful tribe of tooth fairies to which he hopes to belong. As his tale unfolds, however, both What-the-Dickens and Dinah come to see that the world is both richer and far less sure than they ever imagined.
 
- Goodreads Summary