Pebble in the Sky

It begins with a retired tailor from the mid-20th Century, who is accidentally pitched forward into the future. By then, Earth has become radioactive and is a low-status part of a vast Galactic Empire. There is both a mystery and a power-struggle, and a lot of debate and human choices. The originality of the S. F. work is the choice of a very ordinary man as the story's protagonist, rather than the more typical space opera hero.