Dystopias often come in a few, easily recognized flavors: there's the surveillance state, the moral society taken to its insane conclusion, the slowly decaying future that poaches in post apocalyptic territory. These stories rarely reach beyond Earth or into the far future and technological progress has often stopped or actively turned back. While they are collective horrors of all humanity, most technophiles can easily lean back and shift the blame on all those repressive, technophobic people that want to hinder us from realizing our true future, our true potential.
Dark Sky Legion is quite a bit different in that regard. It takes the golden age dreams of space empires, of colonizing other worlds, of meeting aliens and twists them until they have becomes the bleakest, most depressive mirror image of all these hopes. It's the far future, mankind has gone to the stars and realized its true potential. Just not the way you might have hoped.
The Metastable Order is the higher echelon of the galactic human meta-civilization. Its task is to control the development of individual human worlds, to protect humanity in its aggregate against the ravages of entropy and decay. The Metastable Order are big picture guys, who will kill millions if it brings entire worlds back into the fold. Aliens, thought, are not part of the picture at all. The Metastable Order is tasked to realize humanity's fate, there's no place for someone's else.
This fear of change and their readiness to use weapons of mass destruction at the slightest chance of dangerous cultural divergence is born from two elements: space travel is restricted to sub-light speed (act now or there will be no later) and an early conflict in this future history, which nearly destroyed humanity. The reader learns all this not through they eyes of a victim, but one member of the Metastable Order, Maaron Denthurion. When I say victim, I mean only in the most obvious way. Everyone is part of the system, no one can flee to some outside refugee. You can either chose death or being part of it.
The main story is presented two-fold, a recounting of the life of Maaron Denthurion over the eons (he's immortal and copies of him endlessly travel the galactic empire to uphold the Metastable Order) and his present mission. Maaron comes upon a human world that might or might not have strayed too far from allowed restrictions, and his decision can save or cost countless lives.
If you've never read a William Barton novel before, be warned. He's unflinchingly honest in his portrayal of humans. He doesn't shy away from showing the less savory side of human nature and his fiction is not uplifting. It can be tough to read page after page with stuff that goes from bad to worse, with no real light at the end of the tunnel. If you can manage that, thought, you get an entirely original take on the space empire concept with brilliant world building and excellent characterization. Just don't expect a happy ending. That should be obvious by now.