American Demon - Kim Harrison

What happens after you''ve saved the world? Well, if you''re Rachel Mariana Morgan, witch-born demon, you quickly discover that something might have gone just a little bit wrong, that the very same acts you and your friends took to forge new powers might have released something bound by the old. With a rash of zombies, some strange murders, and an exceedingly mysterious demon in town, it will take everything Rachel has to counter this new threat to the world - and it could demand the sacrifice of what she holds most dear.