I think the main reason is that in this novel Angels are full of themselves, really presumptuous, and they are a bit too much sure they will go to Heaven, no matter what; Demons instead seem to not like the idea of Hell (and that is another novelty), and the threat to be killed and going to Hell is something that makes them wonder two time on their action.
Other than the novelty on the balance between Angels and Demons, there was also the fact that this story deals with what should have been ethereal creatures, above Angels, but instead put them in a gritty environment, made even more dusty from the choice of New Mexico: these characters are interacting in the middle of nowhere, far from what we usually consider civilization, and even if it’s not actually underlight, I had the strong impression to feel the hot weather, the sweat coming down from the back, and yes, even the smell. Sometime there was a reference or two to the necessity of a shower, to the fact that one of the character didn’t shave and so on; now in a contemporary setting this would be normal, but we are speaking of Angels and Demons, and so I read it as a way to make them more real, less ethereal.
By the way even the reason why they are in the real world, and not in Hell or Heaven, is due to a more than human action, the launch of the first atomic bomb by J. Robert Oppenheimer at Trinity Site, New Mexico, in 1945.
For this reason, it’s not strange that, aside from an adventure plot, the rescue of an half-breed Angel/Demon, Roberto Chavez, in the New Mexico territory, the main plot is the one happening between Parnell and Navarro. Both Demons and sometime working partners, Parnell and Navarro have also a tentative love relationship developing between them; only that Navarro tends to be the overprotective type, always trying to shelter Parnell from the big bad world, and Parnell is not the one to like being a submissive. Strange is that I didn’t mind Navarro’s attitude and truth be told, I didn’t read him as much as a Macho Man, but more like a man in love who is not used to be weak, since love is indeed a weakness. Sometime I wanted for Parnell to be more kind and attentive with Navarro, like if Parnell was the one in control and not viceversa.
There is a ménages going on among Navarro, Parnell and Chavez, but in the end, I think the real, and long-last relationship is the one between the original pair, Parnell and Navarro, and so the ménages was a nice addition, not an unsettling element.
Amazon Kindle: Trinity Trespass