The Witching Hour (Lives of the Mayfair Witches #1) - Anne Rice
From my notes: Intriguing story with a weak beginning, strong middle, and a WTF ending. Anti-climatic toward the end. For thirteen generations a spirit waits to become flesh and when it does, it runs away with the witch. (This is what I wrote.)

I loved the chronology and the idea of a family controlling the spirit, but the conclusion was not handled well.