There's a lot that could have gone wrong with this book. There seems to be a burgeoning sub-genre of magic noir, some of which totally sucks is not to my taste (I'm looking at you, Harry Dresden), some of which doesn't is (hello John Constantine.) Carey wrote for Hellblazer, so it's not a huge surprise where he got the idea for this novel. Also, this is a sequel. I didn't read the first book, and I wasn't lost or anything. I have a feeling that if I had read the first book, I would be kind of bored by recap. Good on me, I haven't.
Noir is a tough genre, because it's so played out. (No, really. Don't send me threatening emails. The MLA recently issued a press release saying so. Email them.) Anyway, so you're reading noir, and our down-at-the-heel protagonist gets three cases in 24 hours. What are the odds those cases will converge into one big mondo case? And that the protagonist will be beat up like 800x by various competing groups whose motivations are hard to discern? Money in the bank, baby.
Noir is played, so authors add magic to the mix to make things interesting. Now it's not just mobsters and Europeans and Sydney Greenstreet, it's also schismatic factions in the Catholic Church and werewolves and zombies. But the main character is funny, and his inhuman and undead buddies verge on hilarious. Many, many things strain the edges of credulity, but no one ever read noir because they they were looking for social realism. The one-liners alone make this book worth reading.