That would be Marion Zimmer-Bradley’s Darkover series, one of my favs in the fantasy world. The series involves a planet colonized by humans and then lost to humanity for centuries. Some of the inhabitants of Darkover develop psi powers, just as the world devolves into a feudal society.
I started with Thendara House, smack in the middle of the series because it has a nice lesbian love story as the backdrop. That brought back how much I really enjoyed this series. So I went back to the beginning (chronologically)… to Darkover Landfall. If you’ve read Jane Fletcher’s Celaeno series, you’ll recognize the backstory-as-novel approach (Though she handled it as a short addition at the end of one of her books… can’t remember which one). The joy of this is you start at the beginning – who were these people? How did they slip from a technological society into Lords and Ladies (and of course the peasants)?
Mind you, chronological isn’t the only way to read this series. Reading in order of publishing date is very cool as well, as you see the world develop and the author tosses out tidbits (including the tidbits that lead to stories set in an earlier time, chronologically). Either way much fun to be had.
Oh, and yeah, gay and lesbian characters drift in and out of her books… also fun 🙂