Skyler, one of a tiny percentage of humans immune to the plague, is captain of a scavenger ship. He and his crew travel around the world gathering useful materials for use by Darwin's residents and the Orbitals, while they fight off the subhumans, people who have succumbed to the plague. This precarious balance between the Orbitals and the Earth-bound humans, sustained by scavenging, desalinization of ocean water, and space-station-based agriculture, becomes more and more strained, to the point of armed conflict. Skyler is caught in the middle.
Part of me acknowledges that The Darwin Elevator is not high-brow literature, and it may not even be satisfying to fans of pure, hard sci-fi. But in my mind, Hough writes well and provides exactly what this sort of novel calls for: likable but flawed heroes you can root for (male and female), really bad bad guys, cool speculative science, engaging action, and aliens waiting offstage, hopefully to make an appearance in later volumes.
Speaking of later volumes, The Darwin Elevator is book one of three in the Dire Earth Sequence. I like the fact that Hough is releasing the three books in rapid succession. I, for one, am eager to start reading book two!