I had never heard of Silo, but you piqued my interest, so I looked it up. I’m surprised that my SF book group has not brought it up. I see that this is what is called a “pocket universe” story. Since you like it so much, you may be interested in some other stories and a film about the basic idea.
I think Heinlein’s famous story, “Universe” (1941), was the first on this idea, although set on a spaceship (together with a sequel, it appeared in book form as Orphans of the Sky). Much closer, with survivors going underground, is Daniel F. Galouye’s great novel Dark Universe, which was nominated for a Hugo in 1962 but lost to Stranger in a Strange Land; its genesis, however, goes back to a novelette he published in 1952 (undoubtedly inspired by the U.S. missile-silo system). Margaret St. Clair, who was a practicing “witch” (or more precisely a practitioner of “The Craft”), ripped off Galouye’s idea for a very weird novel, The Sign of Labrys (1963), which I don’t recommend.
George Lucas, in his first movie, was the first to put this idea into film, with his classic THX 1138 (highly recommended). Finally, leave it to good ol’ Philip K. Dick to give the idea an original twist, with the government keeping everyone figuratively in the dark by telling them that WWIII is in progress on the surface (while exploiting the population to fund and send troops to the imaginary war, where they are enslaved or killed to reduce the population), in The Penultimate Truth (1964, but based on one of his earliest stories from 1953).