The Postman is a post-apocalyptic science fiction novel by David Brin. It was the basis of a disastrous 1997 film adaptation of the same name starring Kevin Costner (which perhaps should have been titled Dances with Razzies or perhaps Waterworld II: The Land Version).
Gordon Krantz is one of the relatively few survivors of the collapse of civilization. After losing all his possessions to robbers, he finds a U.S. Mail van and puts on the uniform he finds there for warmth. Using it for a con, he persuades the residents of a community to give him food by pretending to be an advance scout for a civilized and expanding "Restored United States". The con gets out of hand, and he is forced to continue the masquerade on his wanderings. It has unintended consequences; as a result of the hopes he has raised, the isolated communities he visits start forging links with each other, and civilization begins to revive based on his lies.
However, the weak new state has to fight Holnists, tightly organized, heavily armed survivalists whose leader has his own idea as to the shape of future society (might is right). Krantz rallies his people and wins the war. Afterward, he learns that the Holnists were fighting on a second front; California it seems has also risen from the ashes.
Best part of story, including ending:
It's believably gritty.
Best scene in story:
To gain entry into one community, he produces letters written by residents of the prior place he visited. Luckily for him, a few of the letters are from relatives of people who live there, building his credibility and undermining the authority of the local petty tyrant. Nicely done.
Opinion about the main character:
Krantz changes from a harmless opportunist into a leader and builder.