Kushiel's Dart, the following series, and then Imriel's, all had such a monumental effect on both my feminism and spirituality. These books weren't just well written, but well researched/plotted from beginning to end with exceptional characters and character development/growth. It's an all time favorite for me, so much so that I have a tattoo from the book and live my life by it's creed: "Love as thou wilt". I only wish I could find more like it.