When an unknown event suddenly shatters the Moon, the people of Earth face the prospect of extinction as the thousands of fragments threaten to rain down upon the planet in an apocalyptic event. In desperation, the world's leaders hatch a desperate plan to transform the International Space Station into an ark that will preserve a fraction of humanity and serve as the seed for its revival. But as events unfold, the astronauts and other survivors face daunting challenges -- not all of which come from space.
Like all apocalyptic science fiction, Neal Stephenson's novel is less about disaster than it is about survival. Readers seeking descriptions of cities flattened by meteors will be disappointed as his focus instead is on his main characters and their desperate preparations for a life after the end. These men and women are generally well-drawn and complex, which helps to invest the reader in the question of their fate, Stephenson add to the challenge two-thirds of the way through the novel by moving events thousands of the years into the future, showing how developments played out in new and interesting ways. Yet the pacing is occasionally slowed by an excessive amount of technical detail, while developments at a couple of key points in the narrative turn on coincidences that are a little too convenient to be believable. In the end, however these issues don't overshadow the overall excellence of the novel, which is a superb example of apocalyptic SF done right.