The cool part was that demons are taking over the world one birth at a time. Humans haven't been born for almost fifteen years, instead, each conception leads to the birth of a new warrior of the demonic regime. I thought this was a really unique idea and felt drawn to how the human race would survive. The author then wove a pattern, which was laid out for the reader early on. It was just watching it unfold for the characters at that point.
There's plenty of classic one-liners, cool twists and military tactics that could keep any action/adventure fan at the edge of their seat. It's also a really quick read. I easily devoured this in half a day. The pacing was well done and didn't stop for an instant.