I know Ursula Le Guin has already been mentioned, but I would like to recommend her also. I don't read a great deal of SF, and I'm certainly not interested in the technology and space battles sort of book.
I think Le Guin is a wonderful writer, and her books are really about relationships and the age-old dilemmas of being human. I'll second "The Left Hand of Darkness" in particular - a great book about understanding the "other". And for a short story, try "The Ones Who Walk Away from Omelas".