The Stone Prince is the first of several set in this universe (and the best, imo). The worldbuilding incorporates fairly standard pseudo-medieval details, but society's roles are (mostly) gender-neutral, for nobility at least. a Duke is a Duke, whether male or female, and you don't see things broken into "women's" or "men's" roles.

oddly enough, I'm just now rereading it - it's been ages since I first read it, and it's held up pretty well.