It's a shame this book did not get more buzz. It will, I believe, become a classic of science fiction in the future. It's almost an old-school SF tale of epic wars and interstellar colonization and space battles and a frightening inhuman adversary, but the grim near-future setting resonates with the anxieties we feel today. Oil wars and environmental catastrophes are what drive the main characters to flee Earth, but they bring all of Earth's troubles with them, and find space is no more hospitable than the hell they left behind. All of the characters are complex and difficult and hard-edged, they all do what think is necessary and sometimes they screw up in epic fashion, and there are always consequences.
It's not a fun read, as most of the novel consists of the struggling colonists experiencing one failure after another, death after death, and their situation continuously going from bad to worse. There's lots of action, but very little victory. If grim and depressing SF isn't your thing, you'll want to skip this book. But the human conflicts are realistic, and it's easy to see humans expanding into space and behaving in just this way. There is a glimmer of hope at the very end, but it's almost buried under the weight of destruction and loss that has preceded it. Nonetheless, I highly recommend this for fans of hard-edged contemporary science fiction.