As y'all may have learned to expect from John Scalzi, this sequel to Old Man's War is quite entertaining. The battle scenes are as good as any in this list: The Forever War Starship Troopers Gateway The Mote in God's Eye.
Though there's a bit too much of 'explaining' the technology and the alien cultures for my taste (after several instances, I skimmed over the rest.), I do not consider this as diminishing the overall likeability of the book. The tone is more serious than its predecessor, an improvement IMHO; the funny scene setups can detract from the story flow.
I enjoyed the book. It's charm lies, I think, in its easy accessibility, the effortless prose and, perhaps, in not taking itself too seriously.
Three and a half stars.