By Joan Slonczewski.
Beautiful, tragic and perhaps frightening, all at the same time.
The Sharers live on rafts on a moon covered by ocean; only the dead sink to touch the floor of their world. Their language is built around sharing: death alone cannot be shared, according to their beliefs. You cannot talk without listening, you cannot teach without learning, you cannot rule without being ruled, you cannot be a deceiver without being deceived, you cannot betray without being betrayed. All verbs cut two ways.
The trouble comes when Valans (from the planet the moon Shora orbits) try to subjugate Shora. There is a fundamental lack of understanding between the two peoples; though some, like Nisi and Spinel, come to be Sharers themselves, the learning is difficult. The Valans are afraid of these people who are not afraid, even of death, and who consider death-hastening evidence of a great sickness of the mind. The Sharers seem a lot like Gandhi with their methods of nonviolent protest, developed over the ten thousand years their civilization has lived to deal with each other. There are also definite echoes of Dune in the way they consider fear and pain. (One of Merwen's theories is that Valans are afraid because they do not understand how to control pain, instead of being controlled by it.)
Despite the above, don't let me fool you into thinking this book is impersonal; it deals very much with people: Nisi the Deceiver, Spinel, Usha, Merwen, Lystra and Realgar, centrally, and others who are still important even if less present in the narrative.
The Sharers science, lifeshaping, is beautiful, just as in The Children Star, or more so: this book gives a much clearer picture of it. The Sharers consider that they have a duty to their lesser "sisters" who share the ocean with them and object to, in part, the toxins the Valans dump in the water to get rid of short-term menaces in favor of long-term ones. They have clickflies which store libraries worth of data and communicate across the planet (though somewhat slowly, as they take time to breed and travel), they harness starworms to give transmit underwater subsonic pulses which communicate much more quickly, and they can regrow limbs and repair genes in living organisms, even if very little of the patient (e.g., the head and part of the chest) is left, if they get there before death.
On the other hand, they also share something called whitetrance, "the most vulnerable level of consciousness", which allows them to choose death at any time, a decision they cannot interfere with.
This book also casts light forward onto Sarai in The Children Star, revealing both much of the background she must have come from (though it isn't entirely clear whether this book takes place before or after, it seems likely to be several centuries or even a millenia or more before) and how unusual she is among her people. Sarai is, incidentally, a very appropriate name; she hopes in The Children Star that no one realizes how much of a compulsion she has to care for children, something which all Sharers seem to share to a greater or lesser degree.
I like this book a lot, but it lacks the real answer to sin and death, though there are parallels. Sharers consider the death-hasteners (soldiers) to be sick children who do not see that others are like themselves, and try to share healing with them, but it is a rather humanistic healing indeed, although there is some mention of souls and the planet itself guiding them. Of course, they also accept death as a natural part of life; Valedon threatens that all will die if they do not cooperate, which all Sharers admit is true, but only when Merwen tries to understand the Valans does she realize that they mean death will be hastened, something unthinkable to the Sharer philosophy.
Anyways--a very compelling read. I can definitely recommend it.