Second in the Old Man's War saga, this book isn't really a sequel. More like a next story in the same universe, with barely one overlapping character.
The tone, the stakes and the rhythm are very similar to Old Man's War though. And while it is an action packed, military action, war-in-space novel, it has time to get deep and thoughtful. The story asks questions about choice, free will, identity and self. These are, of course, hallmarks of science fiction, asking about the human condition by means of putting us out in space and surrounding humans with creatures that understand existence in a whole different way.
I personally enjoyed it more than Old Man's War. The book has time for humour and sweetness, while being gory and violent as well.
I would recommend checking it out if you are in for a fun and fast read and are not too squeamish.