The two great strengths of Aurora, which are a running strength in every KSR novel I've read, are characters who grow, and sensitivity to ecology. The most interesting character is the narrator, the quantum computer running the generation ship, who begins to write a narrative of the ship's voyage at the request of its engineer. As the ship-narrator tells the story, it develops both narrative skill and a personality through the act of telling. It becomes increasingly self-aware and self-reflective, with some delightfully meta sections as the ship muses about the nature of metaphor and other narrative techniques. The narrative structure, the ship's perhaps-sentience, and the material recounted are wonderfully in sync. When the ship's self-consciousness is young, it tells the story simply about the events in the life of a child. As the ship matures, so does the child, and the narrative becomes more complex. Towards the end, there is a big payoff to having the ship as a character, because it can tell the story of complex orbital maneuvers as it attempts to decelerate using slingshot maneuvers. I know, it sounds dry, but it's fascinating and exciting.
Aurora is genre aware, in conversation with KSRs earlier, more optimistic takes on the idea of humans living outside of the earth, as well as, of course, the entire trope of "something has gone wrong on the generation ship." And oh boy, what hasn't gone wrong on the generation ship? In his exploration of the ways that the ecology of a closed, artificial environment could fail, KSR goes further than any SF writer I've read.
It's a big idea book, too, with a clear environmental message, something that KSR goes on to explore even further in The Ministry for the Future, though here it's held together more by the scaffolding of a narrative. It has the best answer to the Fermi paradox I've seen, though to tell you what would be a spoiler.