This novel starts brilliantly, with an intriguing premise, a strange world and culture, and a cast of interesting, complex, yet likable characters. It's unfortunate that it peters out at the end, with a conclusion that manages to feel both rushed and hanging. I get the feeling this might have made a better duology, an idea reinforced by the five-year "jump" that occurs in the middle of the book which, while it ultimately makes sense, is nevertheless jarring.
My favorite aspect of the book is the fact that it presents all sides of every situation, from every perspective. We're first led to sympathize with the Pandoran's refusal to allow refugees to immigrate to their planet, then later to demonize them for it. Likewise, the interplanetary Authority and its representative, Beleraja Poulos, are first painted as bad guys, throwing their weight around and using force and terror to bully the Pandorans into helping them. Later, as we learn more about Beleraja and the situation she faces, we start to respect her courage. Zettel refuses to paint her characters in black and white; each has complicated motivations and conflicting values and it's quickly obvious that there's no "right" solution.
Even the situation presented to the two main protagonists, young sisters Chena and Teal Trust, is fraught with "do the ends justify the means" quandaries. Told their genetic makeup is uniquely suited to creating a cure for the mysterious disease striking colonized worlds across the galaxy, they are nevertheless hesitant to allow the Pandorans access to their bodies. Their qualms are perfectly understandable, yet also selfishly motivated. What if the Trusts could save lives through the sacrifice of their freedom (or perhaps lives)? Would it be worth it?
Zettel, unfortunately, makes little attempt to answer this question. The second half of the book seems to lose focus, dissolving into a confusing jumble of double-crossing. The scenes with the city-mind of Pandora, an artificial intelligence named Aleph, are so full of promise yet so ultimately confusing and secondary to the main plot that we are left frustrated.
Yet overall, this is a fascinating book with a lot of great ideas. The images of the ecology of Pandora are great, as are the descriptions of the unique culture the Pandorans have created to protect it. And Chena and Teal Trust are absolutely believable as adolescents and sisters, flawed yet likable and resourceful. I would definitely recommend this to anyone who likes intelligent science fiction.