Winter in July: (the end of the world...?)

In 2019 many more nations than the superpowers have nuclear weapons and the means to deliver them anywhere on earth.
Kirby Yates, 40, has a good job groundskeeping at the new-construction site of the Energy House Museum at Hammett's Mill, North Dakota, population 240. Kirby suspects the future underground building will actually be a bomb shelter. He's nearly obsessed with that suspicion.
When his mother cleaned out his late uncle's house, then ten-year-old Kirby stumbled onto a collection of nuclear war literature. He didn't understand what he had but began reading and had many nightmares, but couldn't stop reading. He couldn't repress his new found fascination, which followed him into adulthood.
So, yes, the U.S. government is building secret bomb shelters by small towns, the idea being to save entire populations.
After his suspicions are confirmed ex-army Kirby gets a second job (defense of the bomb shelter). But he's unsure of his feelings (hawk or dove?) so attends a peace meeting, where he meets Lisa. She leads a protest at a missile silo, involves Kirby, becomes his lover, and becomes curator of the new underground museum/bomb shelter, but isn't told of its insidious true purpose. Conflict of interest would cost her new job. Novel is character-driven and based entirely from the viewpoint of the civilian, who would hear booms, see flashes, but would go into limbo (the bomb shelter) not knowing who or why.