Since I made it a point to read all the Nebula Award nominees, I might as well read all the Hugo nominees as well. This is one that was nominated for the latter, not the former.
The setting is the late 22nd century, after the collapse of the hydrocarbon economy (caled here "the Age of Efflorescence") has devastated the world. North America is united as a United States where the power rests on a triumverate of the Dominion (a sort of State Christianity) the Army, and a Caesarian presidency. Technology seems to be around the level of the mid 19th century.
The narrator, Adam Hazzard, is explicitly naive, and his naivete colors the tone of the book, making it read almost like a Young Adult novel. Hazzard grown up friends with the title character, who's the son of the president's murdered brother. The two (along with Comstock's faithful retainer Sam) are forced to run from their village, and end up having adventures, up to and including Comstock assuming his uncle's position.
The portrayal of a post-industrial society is somewhat interesting, but I felt it was let down by the cheeseballness of the narration, as well as the clumsy foreshadowing.