Sheri Tepper is a very prolific writer, and her novels are a joy to read: large in size and scope, absorbing, and meaningful. Perhaps because her books have an epic quality, and a strong moral overtone, they have been referred to by critics as "old-fashioned"...in a good way, I think.
Feminist themes are prominent in Tepper's fiction, as the good yam notes, but the stories she tells are not strident or simplistic, as some feminist sf can be, but instead intricate, ambiguous, and intelligent. And in novels like Sideshow she introduces homosexual characters in a sympathetic and totally matter of fact way which warms my heart.
Tepper is also centrally concerned with the environment, and many of her novels involve strong environmentalist messages, with worlds becoming personified as angry beings unleashing violent retribution on the human populations that have decimated a planet's plant and animal life. A number of her books speak against hierarchy and the exploitation of the powerless by a soft, spoiled élite, and show how the powerless and weak can blossom in adversity in a way the élite often cannot.
All of these are weighty and important themes, beautifully presented in highly readable volumes. In addition to all this, though, Tepper can make me laugh out loud with her wry humour and her quirky portrayal of very familiar human foibles. She's a wonderful writer, and I highly recommend her.
There's a comprehensive bibliography of Tepper's work at
http://www.myunicorn.com/bibl13/bibl1307.html