THE FUTURE IS COMPLICATED. As Harry Wilson—the closest thing The Human Division has to a main character—points out, "it's a hostile universe and we should be prepared at all times to kill anyone we meet." That's the cheery philosophy that's been drilled into him; as a soldier for the Colonial Union, he's supposed to be on the front lines of humanity's endless interstellar wars. But for Wilson, things haven't worked out that way: By the time The Human Division begins, the Colonial Union is in chaos, facing a group of unified aliens, the Conclave, not to mention a possible rebellion by Earth. Wilson, meanwhile, is stuck doing glorified tech support for the "band of not-so-lovable losers" onboard the Clarke, a beat-up diplomacy ship that gets the lousy jobs literally no one else in the galaxy wants.

In case all that exposition wasn't a big enough hint, The Human Division—the fifth in John Scalzi's Old Man's War series—probably isn't the best place to jump in. (That'd be 2006's Old Man's War, or 2008's self-contained Zoe's Tale.) For the initiated, however, this Human Division thing is one of Scalzi's best.

I say "thing" because The Human Division was originally released piecemeal, with a new "episode" released weekly and digitally. Now bound together, they create something that's not quite a novel—it's too wide-ranging, too segmented—but not quite a bunch of short stories, considering that a bunch of the episodes share characters, and all of them dovetail in an impressive feat of literary engineering. There's a drawback to the book's episodic nature—exposition gets repeated, a lot—but it's balanced out by the format's freedom. The Human Division is all over the place: There's military sci-fi! There are Nazis in space! Jokes about how terrible the Chicago Cubs are, even centuries in the future! Dog-eating plants! Salinger-esque sibling squabbles! Brains in boxes! Rush Limbaugh, pretty much! A murder mystery? A very patient alien dealing very patiently with those Nazis! "Never a dull day in the lower reaches of the Colonial Union diplomatic corps," Wilson cracks, and he's right: The Human Division's episodes are great, and together, they demonstrate not only how clever Scalzi can be, but also how good he is at thrills, comedy, politics, and making jokes at the expense of the Chicago Cubs. The fact that you never know what you're getting next in The Human Division is one of its perks. An even greater one is how well all those unknowns work together.