The premise is a werewolf accountant who does work for the mob in New York finds himself kidnapped by forces unknown. Leo is hired by the werewolf's daughter to track him down and see if he's alive or dead. This proves problematic as while Leo is a decent enough detective, he's managed to burn every single bridge he's made in the supernatural community. The vampires of the Enclave loathe him as a failed Sheriff, the werewolves despise him as a vampire killer, and the police believe he's a multiple mass murdering hitman [which is true from a certain point of view].
The primary appeal of the story is watching Leo stumble around, offending people left and right in hopes that they let slip something useful to his investigation. What follows is a decent enough mystery that involves the mysterious "Cure" for vampirism that was long ago abandoned as unusually toxic, a sudden upswing in the vampire population of New York, attacks on the mob by forces unknown, and the planned installation of a London-esque CCTV network across the city.
Part of what makes the story work is Leo actively shoots himself in the foot repeatedly by not caring about anything other than himself. It takes awhile for him to put the pieces together because he ignores anything that doesn't directly relate to his case. He's really kind of a cruddy detective as his attitude, cynicism, and nihilism prevent him from developing much in the way of contacts. He has a couple of in a hacker named Mo Money (a self-granted nickname that Leo mocks repeatedly), a morgue attendant, and an incredibly effective lawyer but these are the exceptions instead of the rule.
I think my favorite character of the book is the police office Castillo. Castillo is basically the anti-Murphy for Dresden File fans. She's a dedicated hard-working female police officer absolutely set against our protagonist who seems to get away with murder, literally, on a regular basis. I actually support these two getting together and think it would be a spicy romance. Leo's actual girlfriend, Katherine, is interesting enough but doesn't have the same level of spark.
Does this book have any flaws? Eh, I found it a little weird that we opened up with a perspective other than Leo's at the start of the book despite this being in first person. I also feel like we could have referenced Leo's past with so many characters more. As a vampire, I feel like he would have some more interesting history with various characters. Still, this is a minor set of issues overall and didn't impact my enjoyment much.
In conclusion, I feel this is a solid and entertaining urban fantasy/horror adventure novel. Leo is an antihero that will be an acquired taste to some readers but I personally loved him. I recommend picking up the audiobook novel in particular since the narrator does a fantastic job.