It's whack, dawg.
The first is the Postman himself, Gordon Krantz, who takes the uniform solely for warmth after he loses almost everything to bandits. He wanders amongst small communities performing scenes from William Shakespeare plays in return for food and shelter.
Later, in the second section, he encounters a community, Corvallis, Oregon, which is led by Cyclops, who is apparently a sentient artificial intelligence created at Oregon State University which survived the cataclysm.
Eventually, in the third section, as the Postman joins forces with Cyclops's scientists in a war against an influx of "hypersurvivalist militia", the Postman begins to find that the hypersurvivalists are being pressed from Oregon's Rogue River area to the south as well.
Reviewers are quoted as saying, "it's a book"
Dave Langford reviewed The Postman for White Dwarf #83, and stated that "The story is complicated by Krantz's intersection with another myth in the making, and then by a muddle of battle, murder and enhanced super-guerillas, all a bit of a needless distraction, but never mind. It's nicely written, sometimes moving, and ends as it should. Well worth reading."