Citadel follows up Live Free Or Die with the basic outlines of the universe set up. Humanity is now a minor power, cut off from their galactic patrons by an expansionist empire. Now humanity has to race the clock to get their defenses up before a major invasion fleet comes through.

Our viewpoint characters are Butch, a space welder, and Dana, a shuttle pilot. These is a very guts eye look at mega-scale space construction, as they get the asteroid battlestation Troy turned into a warship. I'll admit, I cackled gleefully when they installed an Orion drive to send the Troy on offense in the final chapter. The bad aliens are delightfully hubristic, the tech big and glossy. Tyler Vernor shows up in a few places to play benevolent overlord, but this is at its heart a blue collar space action adventure.

That said, there's still a lot of Ringo weirdness. Not just the odd jabs at liberals, but stuff like a plague that makes blond women super fertile, or the "hard choice" to doom thousands of third-world contract employees to deaths in space because getting salvage in under the gun means cutting safety regs. And the basic problem of the setting, that Troy is so powerful that even kilometer-long dreadnoughts can barely scratch it, undercut the tension of the battles.