Return From the Stars

"Return from the Stars" is a science fiction novel by Stanisław Lem.
The novel tells the story of astronaut Hal Bragg. He returned from a space expedition to Fomalhaut, which, due to relativistic time dilation, lasted about 10 years. And on Earth, 127 years have passed during this time.
Hal discovers that while he was traveling on Earth, a utopian society, unusual for an astronaut from the past, has developed, without violence and wars.
Hal soon learns that the basis of the new civilization is the betrization procedure, which neutralizes all aggressive impulses in the human brain and strengthens the instinct of self-preservation. However, this procedure also has side effects, at least from Hal's point of view. Humanity is not prone to risk, in particular, space flights are seen as unjustified adventurism. He and other astronauts become strangers to society and even dangerous, since they were not betrized. The main character is faced with a choice: to accept the values ​​of the new society or become an exile...