Aethos v1.0 (2013)

from the publisher's blurb:
Nine hundred and thirty-five years ago, the Aeth attacked Earth. They abducted millions of humans. Not just humans, though. The Aeth arrived with a ship bigger than Earth and took entire chunks of the planet with them, setting them down like sod on the surface of their worldship. They never communicated with us, made no demands, they just did it, and then their worldship slowly accelerated back up to a fraction of lightspeed and with its tiny suns providing light, disappeared into the interstellar dark.

You are a descendant of those original involuntary colonists. Over the centuries, we have discovered that we are not alone. The Aeth remain silent and out of sight, living inside their worldship and only rarely venturing to the surface, but humanity has plenty of company on the surface. Some are friends and allies, some are enemies. Some we have not even met, for the worldship Aethos is a big place and humans only occupy a small part of it. We have recovered and adapted, remembering Old Earth in language and culture, but it is too far away for us to ever return. But more important is that Aethos has fired up its maneuvering drive. It is slowing down, a process that will take a century or more. The Aeth, for whatever reason motivates them, are approaching another star system. Allies who have been here far longer than us say that it is almost certain this system has intelligent life and habitable worlds, and that this is the most dangerous time to be alive. The Aeth will be out and about, hostile races will seek to take advantage of the chaos. Some may even try to escape and find a new home on whatever world or worlds are left when the Aeth get through with them.

Aethos is difficult to pin down as a particular genre. It is a hard SF setting with aliens and advanced tech, but it all takes place on one planet. It is about humans, but does not involve Earth. There is science and superstition, history and legends, open lies and hidden truths, redemption and destruction. It is 200 pages of space opera, exploration, political intrigue, espionage and military rpg setting rolled into one.