Secondly, there are minor spoilers ahead.
The universe of Old Man’s War and Ghost Brigades is familiar to science fiction fans. Humans have technology advanced enough to allow for interstellar travel and the colonization of other worlds. The races they’ve encountered are largely bent on humanity’s destruction, and a team of plucky individuals are probably going to ensure our survival for at least another book (or five). But this basic sci-fi trope is just the framework around which Scalzi constructs his story.
The key to Old Man’s War is, well, just what the title would suggest: the military is composed of old men (and women). Old as in, they enlist at the age of 75. Unfortunately, you won’t be seeing any octogenarians wailing on space bugs with canes. This isn’t Star Wars, so there’ll be no Yoda/Count Dooku fights. But it’s a fun twist on the genre.
World-building is important for me in science fiction and fantasy. If the internal structure of the created universe doesn’t make sense, it’s very difficult for me to get lost in the narrative – no matter how interesting the concept. Here, Scalzi spent a good amount of time constructing the universe in which his story is set, and it definitely seems complex and expansive enough to warrant a six part series. The soldiers aren’t 75-year-olds because we haven’t seen that before, there’s an internal logic that makes sense. The wars fought between humans and virtually every known intelligent life form don’t just happen to justify the danger in which the characters find themselves, the political structure makes logical sense. John Scalzi didn’t just have an interesting idea, he spent the time to connect the dots.
Given the basic premise of this series, that 75-year-olds are used to build armies, Scalzi is able to explore themes of identity that he would go on to explore again in Redshirts. This is especially the case in The Ghost Brigades. There is depth in this story. Scalzi is exploring not only what it means to be human, but how our technology can add nuance to this discussion. Though these philosophical musings may not be the central pillar of his narrative, they are important enough to be more than just background noise.
Ultimately, however, this is a vivid universe with internal logic and a great amount of detail. But Scalzi never gets lost in the weeds of world building. Through the first two books, at least, he keeps a reasonably tight narrative, making for an enjoy afternoon read.