The Doomed City

Andrei Voronin, a young astronomer taken from Leningrad in 1951, wakes up in a city where the sun is switched on and off by someone's decision and nobody can say where the walls end. He and everyone around him have volunteered for something called the Experiment, run by unseen Mentors on rules nobody explains.

He works his way up from garbage collector to investigator to the ruling circle, and the higher he climbs the less any of it makes sense. The Strugatskys thought this was their best book and hid it for sixteen years; it reached Russian readers only under perestroika, and English readers in 2016.