Instruct: Classify a given Amazon review as either positive or negative.
Query: Smart and thought provoking.

This is not quite Simak at his best but it is close.This is a book about human nature, and examines the idea of the pursuit of immortality in a very unusual way.The world here is a grim place with all the joy sucked out of it by hope in immortality, in many ways it is an attack on religion but the religion in the story is scientific.As well as the main plot we see snapshots of the world through little intermission chapters showing the activities of ordinary people.This is a very cynical book, which paints a grim picture made all the more disturbing by how believable it is, a little darker than Simak's norm.The plot is straight-forward enough with a few twists and turns thrown in and the ending is well done.The book is let down a little by the characters, none of them are very interesting, this is really a book about ideas and speculation not characters.A great read but with a more interesting main character this would have been 5 stars.