Like Old Man's War, this sequel has a strong flavour of Starship Troopers. But it's all the good Troopers and none of the bad. It's what I wish Troopers had been - a fun read, compelling characters, mind-blowing future tech, with just a dash of "makes you think" philosophy. You know, without a bunch of self-stroking moralizing about how crime rates are so bad these days because parents don't beat their kids like they used to. 
 In this book, we leave John Perry behind and instead delve into the Ghost Brigade - a branch of the military comprised of the clones of people who signed up to join the Colonial Union, but died before they reached the correct age. These special forces soldiers begin their conscious lives as adults, they know no life outside of the Colonial Union. 
 Unlike the regular soldiers, the special forces are created to be soldiers, and are never given a choice. This provides some very fertile ground to explore the idea of free will and choice - particularly the difference between choices and meaningful choices. 
 Old Man's War did a great job introducing the universe, and Ghost Brigades does an excellent job introducing the overarching plot. I see, now, how the story can be sustained over many more books, and I'm excited to read them.