This one kept losing stars as it went. The broad concept was really interesting, excerpting one of those weird bits of the bible and making it the basis for an otherworldly, fantastical story. But the characters are flat and the writing is dull -- most of the first half of the book is scenes of people doing research, and we get to read right along with them as they examine ancient historical texts and first-hand accounts of angelic encounters. This is about as exciting as reading a musty old history textbook can be, but leaves you ready for some action.
Sadly, when the action finally does start up, the book quickly falls apart. Danielle Trussoni clearly has zero skill in writing a thriller, and the frantic final third grows increasingly ludicrous and difficult to follow, with several poorly-staged battles between demonic creatures and old nuns and an anticlimactic The Da Vinci Code
search for a hidden historical object that is simply there to pad out the story needlessly. The writing is very sloppy and many confrontations don't make much sense (at one point the villain has a gun trained on the heroes but neglects to use it for no discernible reason, even as one of them slowly assembles a mysterious object that might spell the villain's defeat
The ending springs a Star Wars-esque moral choice on the lead character pretty much out of nowhere and the book ends on a very sour note, clearly setting things up for a sequel that I would guess perhaps 10 percent of those who slog all the way through Angelology will actually bother to read.
Oh, and it's going to be made into a doubtlessly terrible movie. Hooray.