Rando Calrissian edited the summary of The Postman Sunday, March 7, 2010.
Despite the post-apocalyptic scenario, and several action sequences, the book is largely about civilization and symbols. Each of the three sections deals with a different symbol.
The first is the Postman himself, Gordon Krantz, who takes the uniform solely for warmth after he loses everything but his sleeping clothes. He wanders without establishing himself anywhere, and acts in scenes of William Shakespeare for supplies. Originally from Minnesota, he has traveled as far West as Oregon. Taking shelter in a long-abandoned postal van, he finds a sack of mail and takes it to a nearby community to barter for food and shelter. His reputation as a real postman builds not because of a deliberate fraud (at least initially) but because people are desperate to believe.
Later, in the second section, he encounters a community (Corvallis, Oregon) led by Cyclops, apparently a sentient artificial intelligence created at Oregon State University which miraculously survived the cataclysm. However, the machine was actually destroyed, and the appearance of it is being maintained by a group of scientists trying to keep hope, order, and knowledge alive.Eventually, in the third section, as the Postman joins forces with the Cyclops scientists in a war against an influx of "hypersurvivalists" (the concept of survivalists taken to a slave-owning, misogynistic extreme—indeed, Brin has said that the novel was, in a way, an anti-survivalist novel<citation needed>), he begins to find that the survivalists are being pressed from the Rogue River area to the south as well. As the story ends, and he comes close to the survivalist's southern enemy, he begins to find traces of them, primarily in the symbol that they rally behind: the Bear Flag of California. The final scenes give the impression that the three symbols may rally together in an effort to revive civilization.
The hypersurvivalists are more commonly referred to as Holnists, after the founder of their ideal, Nathan Holn. Many times through the book, curses are uttered which damn Holn for his actions. Nathan Holn was an author who championed an extreme, violent, misogynistic and survivalist society. Holn is said to have himself been hanged in the novel, but in the time following what should have been a brief period of civil disorder, followers of Holn prevented the United States from recovering from the limited war, and the plagues that followed.
Another message of the plot deals with the backstory of the post-apocalyptic world: specifically, that it was not the electronics-destroying electromagnetic pulses, nor the destruction of major cities, nor the release of various bio-engineered plagues that actually destroyed society: rather, it was the survivalists themselves, those who maintained stockpiles of weapons and ammunition and who preyed on humanitarian workers and other forces of order.