I like Kress and own many of her books. This one held high hopes but ultimately failed due to a shift in focus, insertion of unnecessary comments and an absurd ending. As many have stated, the first half of the book captured the attention of the reader. Sci-fi at its best: the slow buildup, the alien planets, the growing realization of what the Atoners were atoning for...fine.
Then we shift to Earth where we are absorbed with the daily lives of the "witnesses", those selected to venture into space aboard alien craft and observe what the alien race had done to us 10,0000 years ago. We encounter our first logical flaw. Although the vast majority hear the news and go on with their lives, some are so upset that they diligently seek to destroy the messenger. One is reminded of those shows where it is alleged that companies routinely assassinate employees who find problems or emergency rooms in which doctors are engaged in a round of rotating romances with each other. Then there are the unnecessary trivial comments - global warming, health care, "Georgia" voters, religion. Because they were not handled adroitly, they only cheapen the novel, even trivialize it. I call it arrested development; despite inventions, new discoveries, incredible science and the passage of time, folks have the same concerns 20 years from now. We don't even talk about the same things we did 10 years ago!
The ultimate folly, however, is notion that a gene allows us to (**** warning! plot reveal ****) "see the dead". It reminded me of HEROES in which evolutionary changes morphed into such things as invisibility, flying or time traveling. What does viewing dead folks have to do with DNA? As usual, excellent characterization and as usual, the females shine. Soledad and Cam literally carried the book forward. Most of the males were shallow caricatures - Frank, the embittered Catholic, Lucca, the jaded widowere, Fengmo, the every man's gay man.
The ending is two-fold, one good (even great) and one other trite. The appearance of the "aliens" was so hokey one wonders if it was an intentional inside joke. My grade - C+