Kushiel's Dart by Jacqueline Carey

Sold into indentured servitude as a child in the sumptuous and exotic Night Court, Phdre no’ Delaunay is a woman trained equally in the courtly arts and the talents of the bedchamber, but, above all, in the ability to observe, remember, and analyze. She also struggles for honor and duty, and her loyalty to the land she loves will take her to the edge of despair and beyond.