It's been quite a few years since I've read a book with twin protagonists. In this modern day fantasy, fifteen-year-old twins Fiona and Eliot discover they're the unlikely offspring of a goddess and a fallen angel. Their lives in the balance, the two must prove their true natures in a series of heroic challenges and trials. They manage to do these things without coming across as whiny, self-absorbed teenagers, something I really, really appreciate.