I've already lost this review twice because GR was messed up. Maybe the third time will be, as they say, the charm. 
 This book is the first in a series of space opera/military sf. The story takes place hundreds of years in Earth's history and is told in first person narrative of John Perry a pretty nondescript 75 year old ex-advertising writer who becomes a new recruit for the Colonial Defense Forces (CDF). The CDF only take recruits over 75 and all new recruits are given a super, modified, young, new body. Once they have done their time, usually 10 years, they are free to become colonists on another planet but they can never return to Earth. The CDF's job is to find and if necessary eradicate all alien life on these new planet colonies and then protect them from other intelligent alien races that are also looking for planets to colonize. (There is that word again...colonize. This story is very reminiscent of what I know of the slash and burn history and militarism of the British Colonial era.) There is almost no reasoning with other races, the only good alien is a dead alien. Pretty much all diplomacy and negotiation between the alien races has been stopped because the few times it has been tried, it has ended badly. (I found this premise a little to simple and a little sad.) 
 The beginning of the book started a little ho hum for me and the chapters describing when John first goes off world, becomes a recruit, meets his fellow recruits, finds out what it really means to be a CDF soldier, and gets his new body a bit silly. Mostly it is the conversations he has with his small group of 5 or 6 other recruits who become new friends (they affectionately call themselves "The Old Farts" club) that I find a bit banal. These were college professors, scientists and other former professionals and they are talking like giddy middle-schoolers on the first day of the new year at a new school. Maybe that was the author's intention but it didn't ring true to me. 
 Overall though, the story moved along well, was entertaining and well written and brought up some interesting new technological concepts like the skip drive, the BrainPals and smart blood. Every once in awhile Scalzi would start to touch on some of the tougher moral dilemmas and conflicts the characters experienced as a result of these perpetual wars but he never quite went deep enough for my taste. Consequently, the characters were a little lacking in depth. The end was the most interesting part and I probably will read at least one of the sequels to find out if and how the very unusual love story between Jane (the only character I really cared about) and John progressed.