By Judith Berman. Published September 2005 (I guess in paperback only?)
A touching story of a girl who wakes up one morning when she's twelve years old and realizes she's lost something. Most of the book consists of the finding: before that morning, she was a bear, but somehow she has lost her "bear mask" which enables her to take that form... and at first she doesn't even want anything to do with it or the rest of her heritage.
The style is relatively simple, but fluid and cohesive. I think this could probably be in the children's section. An interesting mythology and an angry heroine who, I think, grows up along the way lead to another happy ending. I seem to be having more luck with these lately, don't I?
Drawback: The story never really answers how she lost her mask (or at least implies that there is more to it than the simple answer heard in the first chapter.) But, this isn't a big lack considering everything else that happens.
It does contain reincarnation in a rather tangible form, along with spirits and other (apparently) Native American beliefs.