The sequel to These Broken Stars, though I don't think there will be spoilers ahead for that. The main characters aren't even the same. It opens with Captain Lee (short for Jubilee) Chase at the bar Molly Malone's (Molly being a 300-lb Chinese guy) and trying to appraise a new guy, who is obviously not a new soldier assigned to Avon. They speak, and he abducts her at gunponit, because she comes too close to the truth: he's a Fianna, one of the rebels living in the swamp.
He takes her east, demanding to have an explanation of why there's a secret base. When they reach the island in question, there's nothing there. Except that when they are leaving, Lee sees, just for a moment, fences and buildings. He takes her back to the Fianna lair, where she learns he is Flynn Cormac, the brother of Orla Cormac, executed for leading the revolt ten years ago. It gives him some moral standing among them -- not enough to take on those who want her dead.
This all adds up to a story that included the id chip Lee found on the island, showing something had to be real, the story of Osinn and Niamh, Lee's old commander and how he and Flynn nearly come to blows when they meet, the Fury that takes over the minds of soldiers, how orphans are shipped to orphanages on other planets to prevent their being raised as rebels, how Avon's sky is always cloud covered, why Lee doesn't dream, the way certain guns keep history of the times they were fired, and much more.