From the back of the book:
A Far-Future Passion Play
It is the sixth millennium. Humanity spread across the stars and built a republic of advanced technology and universal emancipation - and then squandered it, fought over it , and lost it. As the light of the stars began to slowly fade, a New Dark Age descended upon the Known Worlds. Then, from the ashes of war and ruin, Emperor Alexius rose to power and ushered in a new era of hope. He calls now for brave knights, wise priests, and resourceful guilders to bring his peace to all the worlds, known and unknown.
The Universe Book presents the setting for Fading Suns: its history, society, and astro-geography. Herin you will encounter nobles, priests, guilders, aliens, psychics, cyborgs, and more.