The Ghost Brigades departs a bit from Old Man’s War, being the rare series that switches main characters between books. Whereas the first book was a narrow, Starship Trooper-esque novel, The Ghost Brigades starts to expand the world building. We get to see humans and aliens do much more than shooting at each other this time around. Politics both inside and outside human culture start coming into play. It becomes more apparent here that things are not as simple as “humans good, aliens bad”. This is like the Rogue One equivalent to the series, where we see the good guys doing some definitely unethical things in order to win.
New protagonist Jared Dirac is fairly different from John Perry in the first book, but still a fantastic character. Being able to showcase an equally good story using someone with a very different personality really showcases Scalzi’s writing ability. For reasons that would contain spoilers, Dirac starts out with an almost childlike personality. And is immediately thrust into the life of a special forces soldier. He picks up traits from his brothers-in-arms, but his core personality persists throughout the story. It adds a unique nature vs. nurture aspect to Dirac and to the story as a whole.
The first book highlighted that essentially all aliens (and humans) are in a constant, all-out war. Habitable planets are extremely rare (which itself is rare for a series like this) and everyone fights for real estate. But here we start to see that there is some trade and some aliens are willing to make alliances. Not forever, but long enough to crush a common enemy. And humanity has been successful enough in its conquests to make many, many enemies. At the same time, though, old hostilities and habits can make “allies” quick to turn on each other.
What really sets The Ghost Brigades (and Old Man’s War) apart is that it is pure, military sci-fi. There are hardcore action sequences, but there is also humor. Politics play a part and so do the everyday lives of characters who know they are cogs in the machine. Scalzi manages to write all of this around a host of interesting characters, some new and others returning from the first book. All the while, he keeps things focused without turning the book into a space opera or some other sub-genre. Not to say space operas and other genres are bad, but keeping that rare focusing is a large part of what elevates The Ghost Brigades from good to great.