A fine collection of short stories and novelettes including several using the idea of parallel universes. The author does a better job than most of meshing the hard SF ideas with interesting characters in more or less plausible situations. He also pays attention to the emotional impact the story has to deliver. A few of the stories seemed to be just the kind which were tossed off, but the best of the collection pose intriguing ideas in a stylish fashion. ( )

Like most single author anthologies, this set of stories is a mixed bag. The title story ("Ten Sigmas") is a multiple worlds story about a set of identities spread over multiple realities that tries to save a battered woman seen in a glance. Some of the identities ignore what they saw, some die trying to save her, some die when no one is there. It is a well structured tale, but slight. "The Teosinthe War" explores the question of using multiple worlds to test the theories in Germs, Guns, and Steel. An excellent premise, but not solidly welded to the weak romantic subplot. "Doctor Mighty and the Case of Ennui" is an amusing exploration of comic super-heroes everywhere.

A strong series of stories is "The Summer of Seven", "Singletons in Love", and "Strength Alone". The author has envisioned a future depopulated by the removal of billions in a possible Singularity Event. The humans who are left are mostly multiples, groups of individuals joined together through pheromones and bodily secretions, that allow several people to act as one consciousness. The description of this world and the plight of human individuals that often feel less than human without their "pods" of others, is a wonderful depiction of individual and group strategies.

The strongest tale in the anthology ("Walls of the Universe") won the Asimov's Readers Poll for Best Novella and was nominated for many other awards. This is a tale of John Prime who has a device that will take the wearer to another parallel universe. He tricks John Farmboy into using the device and takes over John Farmboy's life hoping to make billions with devices invented in other worlds, like the Rubik's Cube. Meanwhile John Farmboy is stranded in other parallel universes and unable to return home. This is marvelous investigation of nature versus nurture that elicits many more questions that it solves.

Overall, this is an interesting insight into a growing SF writer. I look forward to reading more of his stories and novels in the future. ( )