In "Angels" I think Denis Johnson is focusing on the mystery of being a particular self, and questioning how much of the stuff that goes together to make a self is actually that person's own doing. His vehicle for this exploration is the underbelly of the USA, and here he taps into a tradition in American writing stretching through Kerouac, and Fante, Bukowski, Miller and Dreiser, and no doubt many others unfamiliar to me; in a way, a more distant echo is heard in Beckett and his tramps. The wonder of individual consciousness, the experience of subjectivity, is illuminated by making all the gaudy trappings of the world dark.
I've read criticisms of "Angels" bemoaning the sketchy take on the central characters, but I disagree that this is a failing. Johnson gives us enough for us to sympathize and, at times, empathize with his motley cast, and certainly enough to share in their everyday epiphanies, when they see the world fresh and new and each moment appears precious and, by the miracle of Johnson's poetic prose, we see out of their eyes.
Likewise criticism falls upon Bill Houston's fate as being somehow unemotional, but this very fact suggests that we are not simply being asked to consider the ethics of capital punishment, but also to dwell on our own, that is to say everyone's, inevitable fate - the blind certainty of our mortality.
The entire work questions the role of personal will versus that of circumstance in deciding the choices we make. I do not think that a pat answer is provided, instead the question is raised and investigated through the thoughts and deeds of Johnson's miscreants.
All of this is dressed in Johnson's universally praised and delicately wrought language. For me, this novel is a celebration of the power of words to first and foremost communicate - if we gain a window into the souls of "Angels"' lost protagonists, then how much easier to see inside our own, and inside those who surround us.