Despite angels and demons, the book felt curiously bland to me, and apathy neatly sums up basically my entire reaction to the book.
When I read it, I had not yet really read many "urban fantasies" and found the idea of suit-wearing angels strange and unwieldy. Basically my opinion was that if you write fantasy, then write it--you should at least create a hidden realm where your imagination can go wild. I saw "urban fantasy" style novels as a lazy mishmash of our current culture and mystic special hidden powers. I've revised my opinion and greatly enjoy the "hidden society within our own", but I still have issues with supernatural societies where the supernatural seems to have little impact on everyday life.
I'd like to reread it at some point, because while at the time, this book felt to me to beggar belief while still remaining too close to reality for me to handle, I'm curious as to how it would strike me now. As one might have guessed from the title, there are angels in the book. The author spends what to me felt like an egregious amount of time describing their wings, which can be, as far as I recall, about thirty feet in length. The wings are simultaneously tangible and intangible. While reading the book, way too much of my brainpower was diverted to skeptical thoughts related to the feasibility and physics of this.
The major selling point for me is always characters. If I find the characters fun, believable, and likable, I'll forgive almost any flaw in logic, reason, and worldbuilding. I felt that this book simply did not have any character that could save it from mediocrity. I found the villain somewhat interesting, analytically, but the protagonists were so dull that I could not rustle up any concern for their well-being.
To me, the characters felt flat, the writing felt choppy, and the narrative didn't seem to flow. It felt like someone transcribing the events of a movie in a "and then he did X" kind of way. Funnily enough, the book apparently was optioned as a movie before it even came out as a book. I guess the producers thought the same thing. While as a story, I felt that the mythology and characters were painfully underdeveloped, I really think the idea can be turned into a great action movie.