"A thousand years later, humanity's last empire is on the verge of collapse," reads the introductory text to the Alliance of the Sacred Suns, which is a good introduction. The great science fiction strategy and the hybrid 4X have a new demonstration on Steam, which you can play right now, where you take on the job of a new emperor or empress responsible for maintaining the disaster that is the future of humanity to get worse.
It is a unique playing field, a strategy game where the player cannot micromanage his empire, but must use personal relationships with powerful people and politicians to govern. Putting people who trust you and trust you in positions of power is how things are done, not commanding individual fleets.
Your goal is to prevent the fall of humanity in a dark age, restoring the strength of your imperial house and central government, while other noble houses are just as happy to strengthen themselves. Of course, not only other humans care. Foreigners can see that humanity is weak too.
If, like me, you see the 1997 parallels Emperor of the faded suns, make no mistake. Both games are definitely inspired by the spatial feudalism of ancient science fiction, such as Frank Herbert's Dune or Gene Wolfe's The Book of the New Sun.