I tend to think of Kress’ books as character novels. The plot is secondary; it’s there as a device to help us understand the characters, their motivations, and their inner lives. From that point of view, this is quite a successful book. It focuses on a small group of people who are chosen to be “witnesses” after an alien race (calling themselves “the Atoners”) recruits humans to go to other planets and, well, witness what they see.
The “other planets” turn out to be populated by humans, although there are some key differences between Earthlings and these other humans. The others, you see, can communicate with the dead– the Atoners are atoning for having genetically modified Earthlings to remove that ability.
This sets the stage for a complex set of interactions between several of the witnesses. The richness of these interactions, and the characters, is what made this book a success for me. I don’t want to spoil it by telling you too much about them; it would cheat you out of discovering the characters if I explained them in too much detail.
Recommended, provided you’re not looking for a hard SF space opera or a plot-driven joyride. This book is neither but it rewards the thoughtful reader.