Earth is uninhabitable, and the surviving humans now live on New Earth with the technological assistance of the alien Kmet. One day, a message from a faraway human “sleeper” ship throws both human and Kmet into a frenzy; the humans are delighted to reunite with their long-lost family, but the Kmet seem to have problems. Henry, the arbiter between humans and Kmet, must turn all his faculties to understanding the Kmet while preserving humanity; his pilot, Killian, turns her natural suspicion into a mission to understand what makes the Kmet tick. The book unfolds very slowly but speeds up as you go, as the humans gather more clues against the clock of their species’ destruction. Extremely inventive alien biologies and life cycles; great exploration of scenarios where one must make morally problematic decisions. The characters were really well fleshed-out and kept the book from being too much of a thought experiment in places; the secondary characters and relationships were fantastic as well. Fans of Adrian Tchaikovsky would like this, I think.