John Perry enlists with then Colonial Defense Forces. Which is to say, we're doing another military sci-fi, but in this case, the enlistee is 75 years old.
Whatever magic or technology the CDF has, they only take older people. By then people are old, your friends (and maybe a bunch of family are dead) and the CDF can offer you young life and honor serving to protect human colonists on other worlds. You don't know how this happens, you sign up and agree to effectively (and legally) die on Earth and go to the stars.
I like this premise, it's interesting. It's interesting to think about whether or not you would make this choice, to think about how experienced people would surely make better soldiers than rash young (teenaged) men and women.
Perry goes through basic training and starts his service. He discovers that there are only a relatively small number of habitable planets and a whole lot of alien species willing to fight us over them. His cynicism gets cynical and he deals with the brutal day in and out killing of creatures (the Lilliputian-like Covandu crack me up *almost* as much as the Consu; to be fair, I probably would have lost some of my soul with the Covandu as I did do my best Godzilla impressions) of different types and sizes. He does fairly well, being able to think while carrying out his orders and pay attention to things around him many of his fellow troops miss.
In the end, he does fairly well, and seems to not lose too much of his mind in the process.
You can feel the influence of Starship Troopers, most definitely, in this book. I'm not feeling Forever War (or any other military sci fi) nearly as much, which is fine. And I really do feel like it stands on its own in military/space opera sci-fi ranks.
I just really wasn't feeling the non-stop witty banter of the geriatric recruits. I get that they might act juvenile, but the constant banter. Argh. And to be honest, I like Scalzi's (witty/thoughtful/intelligent) writing, but I have to be in the mood for his catchy banter. I was not when I read this book.
Sadly, I almost liked this as much as Starship Troopers, but not quite. That kinda cracks me up, because I have a hate-on for Heinlein, and I adore Scalzi. If only I could make my opinions of writers reflect how I feel about the book. Oh well.