Lois McMaster Bujold. Space opera that's so character-driven that people who claim not to like SF have enjoyed it, but with some intriguing speculative elements, too. (She's the only person I've read who's handled a one-sex planet believably, for instance.) And in my opinion, Miles Vorkosigan is the single best protagonist from any series ever.

The Warrior's Apprentice (or omnibus Young Miles) is a good starting place. She writes fantasy, too, and has done more of it lately, but it doesn't grab me quite as much as the SF.