A post-post-post apocalyptic, post-singularity galaxy settled by transhumans, where humanity is waning. Distinct intelligence is dying, as human society is too spread out and separated, with thousands of lives ended by ennui and many more destroyed by Berserker Probes. A few dozen billion lives are spread throughout the entire galaxy.
Faster than light travel is horrendously slow, communications are limited to radio, in-system neutrino communicators and quantum blueboxes. FTL sensors allow you to see the distant travelers on the horizon, and the ships that pass you in the night. Individuals traveling between pockets of civilization might not see another living being for centuries.
The driving plot will be a romance between an asteroid miner (who styles himself a swordsman), and daughter of a Sleeper ship captain (who acts somewhat akin to a princess).
Humanity spread throughout the stars, sending out terraforming probes known as Formers to seed it with life. A thousand generations passed before humanity began venturing out themselves to colonize many worlds in vast sleeper ships. The Earth, choked by the vast megastructures required to keep tens of billions of people alive, was abandoned as a monument to the tenacity of humanity, and a reminder of the cost of their continued survival, while the colonies on Mars and the moons of Jupiter and Saturn would form the core of a provisional human government until the new shape of human society revealed itself.
Colonies were founded as near as Alpha Centauri and Sirius, to the very edge of the Milky Way, following the distant trail of the Formers sent out by their ancestors.