Isaac Asimov wrote this book in 1949 when he was in his twenties and launched an amazing string of science fiction novels. His spectacular career lasted until he died at the age of 72. Pebble in the Sky is, as they say in the music business, 'a golden oldie' that is well worth reading. I have not read any of his works in several years and decided on this particular novel after hearing a recommendation on a podcast.
The story begins with Joseph Schwartz walking down the street in Chicago. In an instant he is transported to the distant future where Earth is part of the Galactic Empire, but ruled locally by an ultra-conservative theocracy. Much of the planet is radioactive and the citizens are only allowed to live until age 60 in order to keep the food supply and population in balance. Everyone must carry identification and have a unique number. Joseph is taken to a famous scientist who is conducting brain experiments, since the people who found him don't know what else to do. The story moves quickly from that point and takes some very unusual turns. Those of you who have read the Robot Series and the Foundation books will find some some familiar themes in this novel. Check out Wikipedia for a good summary of the author's professional, scientific, and literary life.