One day nearly all humans disappear from earth as an experiment by God. The few men who were left behind now live for 5000 or more years without sickness, but the earth has been depleted of its resources. However, without a dependence on technology to hold them back, the humans left behind on earth learn teleportation and telekinesis. Strangely, it's the robots left on earth along with an alien visitor who search for communication with God and the way to secure a soul for themselves. Unexpectedly, a rumor circulates that the humans who disappeared from earth so many years ago are on their way back to earth ...
I definitely enjoyed this book. I'm not so sure why so many people gave it low star ratings. It's classic Simak.