Zelazny successfully weaves a tale of the far-future in which a form of quasi-immortality is achieved by transferring one's mind to new bodies. The ruling elite utilizes a mindreading technology to review the quality of one's life, and this is used to reward or punish a person with either a better or worse form. In effect, science has discovered the means to mirror the Hindu concepts of karma and reincarnation.
These technologies are used to solidify the power of the Deicrats, the ruling elite of the planet. Morality is secondary to how well one supports their grip on power. Those who oppose the structure are destroyed. Those who are in power, the ones who hoped to style themselves after gods, are driven by the same dark emotions that have powered mankind through history: ambition, jealosy and greed. This story is about Sam, a man forced to choose between joining with this system of power, or rebelling against it.
While this is a relatively short book (by modern science-fiction standards), it is also dense reading. Slogging through the first chapter and a half is necessary before things really start to click along.
This is a novel that is rich with ideas. It demonstrates the harm that can be caused by caste systems borne out technological haves and have-nots. It portrays the classic theme of "absolute power corrupts absolutely," but also shows that goodness exists within a few humans to oppose corruption. It does both of these against a unique, Hindu-inspired backdrop supported by the necessary science.
Your enjoyment of this book will probably be driven by the type of science-fiction reader you are. If you want something heavy on ideas and milieu, you will probably love this. If you want something that is more character-driven, this may not satisfy you as much. Despite its shortness, you may find yourself downshifting your reading-gears: dialogues often consist of a dozen or more lines of unattributed text--and characters don't speak in particularly unique voices. Some characters are known by multiple names, which I found initially confusing. Despite this, I can't imagine that anyone interested in speculative fiction could be fluent in the genre without exposure to this fascinating tale.