Probability Moon by Nancy Kress is the first book in the “Probability” trilogy and is followed by Probability Sun and Probability Space. Kress is probably best known for her novella Beggars in Spain, which won both the Hugo and the Nebula awards in 1991, and evolved into an entire trilogy (review). The first two novels in this series, Beggars in Spain and Beggars and Choosers, were nominated for both Hugos and Nebulas for best novel but did not win either, although Kress has won 4 Nebula awards for her novellas and short stories.

Probability Moon takes place in the distant future. Humans have found a method of traveling throughout space, but during their explorations they discovered the Fallers, an alien race bent on their destruction. Soon there is war between the two races and humanity is facing extermination–until they find a new planet and realize one of its seven moons is not a moon at all. It is actually a manufactured object, perhaps a weapon to use against the Fallers. Scientists are sent on a secret mission to study it under the guise of observing the aliens living on the planet, who are unusual in that they “share reality” and experience physical pain if they do not all share the same beliefs. A team of anthropologists is sent to study the aliens, completely unaware of the real purpose of the mission and the fact that the rest of the ship’s crew will be examining the “moon.”

Enli, a young female, has been declared “unreal” by Reality and Atonement for the murder of her brother. Now she is an outcast since all the “real” people must ignore her while she works to earn back her right to be a part of reality and have a proper burial for her brother, whom she cared deeply for. When the humans come to her world, she is assigned to spy on them and gather information allowing the aliens to decide whether or not the humans are real or unreal. If the researchers are found to be different from the aliens, they will be killed, according to the traditional penalty for those who do not share reality.

The alien race in Probability Moon was very well done and I hope the next two books in the series contain more about them. Having a uniform belief system is an intriguing idea – it sounds horrible (and rather dull) in one sense; however, when the people all share the same worldview, it results in no disagreements and no war. Yet the pain is not the only method of controlling shared reality since the unreal or children who never grow up to exhibit signs of being real are executed, which is a rather harsh price for keeping a peaceful community.

There were several characters the story focused on, mainly the anthropologists studying the world, the military team on the ship studying the moon-artifact, and Enli. None of the humans were particularly well developed, although I did find David, the young and inexperienced man who became part of the expedition only through the influence of his father, rather interesting and the best developed of them. David believed the aliens and their shared reality was far superior to humanity and wanted to learn how to genetically modify humans to have shared reality, envisioning himself as a hero who would create peace on earth. The unreal alien was the most real and sympathetic character in the story with her sadness about her brother and wish to be accepted and redeclared a part of her people’s reality. I would like to know more about the details of what happened to Enli and her brother as well as more information on why she was declared unreal but not killed.

This book was a little slow to start with, other than the chapters about Enli which captured my attention from the beginning. I did find the parts that took place in space particularly hard to read early in the novel, but they became easier to read as the story progressed and this was the storyline that had fewer pages dedicated to it.

Probability Moon is a thoughtful novel about two very different races trying to learn about each other, as well as humanity’s quest for knowledge that could save them. Recommended to fans of first contact stories and those who enjoy imaginative science fiction.

7/10