Kelly Gay jumps right back into the world she left--just days later in story time. Atlanta has undergone some big shifts: there's this whole cloud-of-darkness floating over the city, for example, and the level-one boss from the previous book has checked out. Taking his place is a serial murderer, and it's up to our dynamic duo of MCs to find and stop him.
This book doesn't bring in much additional novelty. We revisit the Djinn, which is fun but not really new since they were covered pretty well last time. We get to see our buddy cop the Siren pull off some big magic, but again that's been seen before. The MC's sister is addicted to a nasty magic+drug combo, but that was the result of book one's plot. OTOH, even though the world hasn't expanded much it's still rich enough to justify the additional interior exploration.
Another thing that hasn't changed much is the MC, Charlie Madigan. I'm hoping that's the result of the short story-time between books 1 and 2, rather than the author's inability (or lack of desire) to let the character grow and change. Take the Dresden series for comparison--and yes, I'm biased since I love that one: the MC there grows and changes significantly from book to book, and his compatriots grow and change with him. I really want to see some of that happening here.
That's all kind of bumming, but it's not particularly bad. The yummy part is that Gay manages to keep the light-and-fast thing going again: action interleaved with drama and plot twists, a few minor novelties thrown in just when you need them. The pacing is very good and turns this into a fun read, with a satisfying dénouement--that last bit being a welcome improvement, since the last one's epic clash was so very, very flat.
So, as with the last one, this is a fun but not really compelling book. I'll be buying book three, but if the characters don't get their growth on and the author can't expand the world into new directions, I doubt I'll read book four.