Bobby Dollar is an angel who isn't particularly angelic. He's cynical, swears a lot, gets into epic bar fights, tells the occasional untruth, pines after demonic women and questions the existence of god and Heaven.
Usually, writing a book in first person can get dull - only having one perspective can make you want to rip your eyes out if the character has less personality than trigonometric functions. Luckily Tad Williams' character Bobby is a pretty cool guy. He's funny, quite charming in a "I can't believe you have the audacity to say that" way and too curious for his own sake.
It's Bobby's curiosity that gets him into trouble really. His angelic duty is to act as a heavenly lawyer and defend dead souls when they are judged to go to Heaven, Purgatory or Hell. Unfortunately, Bobby's life becomes violently chaotic when a dead soul magically disappears and he decides to investigate; it doesn't help that Hell thinks that he's stolen the soul!
Despite the whole Heaven and Hell thing, the story is not at all preachy. There's no preference towards a particular religious order (thereby neatly avoiding offending anyone). Through Bobby's eyes we see that Heaven isn't quite as perfect as it is made out to be and not all of Satan's servants are crazy evil. It's impressive that Williams managed to pull off moral ambiguity despite the black and white nature of the stage his story plays out in.
I really can't wait for the next book, especially as (part of) the story will be set in Hell.
As an aside I actually, quite embarrassingly, thought that the city Bobby lived in (San Judas) was a real city. The descriptions were vivid, but the main reason for believing in the existence of the fake city was the historical excursions the character made every so often. I guess my exceptionally poor knowledge of American geography is also a big factor....