I really liked this, and need to ponder some of its themes some more: what does it mean to be human, and what is our purpose, and how much risk is inherent in just living your everyday life (and how do you feel about that?). Basically, it is set after humans have evacuated a toxic and poisoned Earth - there is a mission back to investigate the status of Earth. I don't want to say too much more, because the plot unfolds very neatly, and I wouldn't want to ruin it. (But I can't help myself: the Beastship is so cool!)