I've never been fond of space operas, but I really liked the ideas behind this novel. The elderly fight the good space fight in exchange for being made young again and, if they survive their years on active duty, a second lease on life on one of the colonised planets.
The trouble lay with the characters, who, while varied in their backgrounds, all had the exact same voice. It's a case of "too much snark" and "is that really something a septuagenarian would say?" I was easily distracted from this grievance by the alien battles (which were great), but there's only so much dry sarcasm that a person can take.
'I did two things on my seventy-fifth birthday. I visited my wife's grave. Then I joined the army.'