Book is OK. Not brilliant, not as fun as the Dresden Files, but OK.
Dark, dry, cynical humor. Overuse of metaphors, every other sentence. The 'exorcise with music' is straight from Garth Nix's books. A lot of "Pratchetisms", sometimes almost outright quotes without a nod to the source. That irks me.
The feel of the book's worldbuilding is nebulous and sketchy, but original. I like what he does with zombies and weres. That's outright fresh in this genre. I want to know more about it.
I don't think the book is all that dark and gritty. People who call it that obviously never read dark and gritty books. Try Donaldson's later works and Erikson's to see what I mean.
The series has promise (Jim Butcher's "Storm Front" wasn't exactly brilliant writing either, even though it was a *lot* more fun and was chockfull of memorable quotes), so I'll give the second book a try.