The novel explores the fate of the human race after a mysterious 'Agent' shatters the moon into several pieces and renders the earth uninhabitable. The book can be fairly neatly broken into three sections: we meet the main characters watch as the world plans for survival in space, then we follow their experiences post-destruction as they adapt to life without their home planet, and finally jump forward five thousand years into the future as the descendants of our protagonists are planning a return to the earth. It is clear that Mr Stevenson has done his homework. There are reams of technical monologues in the book and whilst you might enjoy them if you have a keen interest in the deeper concepts of orbital mechanics, DNA splicing or robot swarm theory, I had to skim the denser description whilst hoping that I wouldn't miss something crucial to the plot (I didn't).
On the whole this was an interesting take on a very feasible future for the human race and anyone that enjoys post-apocalyptic fiction and hardcore sci-fi should at least give it a look. Just don't get too hung up on all the technical stuff.