I watched the first episode of the tv show based on this novel. At least, I watched part of the first episode, I don't remember if I saw it end. I must admit that from what I remember of the tv show as compared to this book, I definitely prefer the book. Goodness, what a surprise! There are very few cases where I actually prefer a movie or television adaptation to the book.
Having the protagonist be a serial killer is not usual in crime novels. Particularly ones that focus on the investigation and the team of police involved. It makes a nice change to see things through a double lens. It also allows one to experience murder through the eyes of a killer without it being the murder perpetrated by the guy that the police are trying to catch. I like to get both perspectives, but don't particularly like having knowledge about the 'bad guy' that the police/investigators don't have. It just frustrates me. Having one of the cops be a serial killer vigilante seems to solve that problem nicely.
I can't say that I didn't see the twist at the end coming, but it was enjoyably done and well-written. I don't know what the rest of the series is like, but I'll be keeping an eye out for them. This is definitely one that I'd recommend, though I imagine that it would be a different read if I'd watched enough of the tv show to know exactly what was going to happen all the way through.