Dystopian literature: it ain't pretty. In fact, it's downright ugly. It's the opposite of everything pure and good and beautiful—that would be a utopia, folks—but it definitely seems like it's a lot of fun to write.
Horrible brain viruses. People burning to death. Women eating cats. A lot of this book reads like the transcript of Dashner's nightmare journal.
But let's get down to brass tacks: The Maze Runner series is a dystopian series. But The Kill Order gives us a look at how it all started, how the world really turned upside-down.
Dystopias usually have some kind of catastrophic event, or at least a bad event happens to start things rolling (toward hell). In this case, it was the sun-flares. This natural disaster is recounted in Mark's memory-dreams, and we get to see the full horror of it—we see the massive death tolls, as well as the destruction of the world's landscape.
But the sun-flares are only the beginning of the dystopian problem; it's actually the release of the Flare that really gets things going.
The Kill Order is our ticket to seeing the very start of the show: first we see the natural disaster, then we see the man-made disaster (as well as what prompts the man-made disaster). We get a front-row seat to the end of the world… and the end of the world makes The Maze Runner look like a walk in the park in comparison.