I really waffled on how to rate this book. It's got a lot of components that I really like, and a nice little ending that I felt worked really well. But at the same time, I think the gumshoe detective angle was a bit too... spot on, I suppose, for me to enjoy this as much as I wanted to. 
 And I did enjoy it, make no mistake. The archangel Gabriel has been murdered, and all of heaven is in free fall. Our intrepid Detective, Bayliss, is least among the angels, but finds solace here on earth, hanging out with the monkeys. When Gabriel is murdered, he has to find someone to replace him, fast, before reality breaks and all is lost. So, he picks a drug addicted guy in a dark alley, follows him and his sister to a train platform, and arranges for an accident that will kill the sad guy and promote him to an angel. No fuss, no muss. 
 Except he accidentally kills the sister. Big mistake, as Molly isn't like her brother, she's going to figure out what's really going on. And hope that whatever out there that is powerful enough to be killing the angels doesn't decide to take care of her next. 
 Really, a great story, and Molly's portions were the highlight. I get the feeling that author Ian Tregillis, really wanted to write a detective story in the old, classic, mode. You know, "A dame walked in, she had legs that went from here to the moon, and gams that would make a melon farmer blush.' 
 And while that's not a direct quote, you can hopefully see why that got tough to get through after a while. It was really tough, honestly. It actually turns into a plot point later in the novel, but that doesn't make it any easier to read. So, I'd give 5 stars for the story itself, and maybe 3 for the fact that I had such a tough time deciphering 40's era noir talk, which was made at least slightly tougher with all the physics related one-liners that Bayliss also spent a lot of time spewing. 
 Oh, I'd forgotten that, yes, now try to picture that same detective with the annoying affectation in his speech patterns giving a lecture on quantum mechanics. 
 So, read if your love your angelology wrapped up in a noir novel with tons of quantum physics peppered in. If those aren't your things, you might need to pass. But for me, I really did enjoy it. And I have no idea if there is a sequel planned, but in what appears to be something of a novelty nowadays, this acts like it's a stand alone novel. It tells, what I think, is the complete story. Well done.