My boyfriend and I were talking about books and he mentioned one that used to be his favourite, but he doesn't remember the name. I thought it would be a cute present to get him for Valentine's day, but the whole don't-know-the-title thing is going to make this difficult. Can you help me?

Here is what he remembers:

It's a fantasy novel. In this world, there are humans and mythical creatures. They're referred to as inner- and outer- . . . something. The main character is a witch police officer. She uses charms, primarily. Her police partner is some super-sexy vampire woman, whom in which everyone is attracted to, even the main character at some points. The main character also has a friend who is a fairy or faerie, I don't know which, and he has a rather New York type personality. At some point, the main character is investigating a mob boss and that angers him, so he goes against her. The book is AT LEAST three years old, since that's when my boyfriend remembers reading it last.