I think I read Graceling first, then Fire, then Bitterblue. I definitely preferred Fire out of the three, because I thought that in comparison to Graceling it was very tightly focused on the theme of human nature and relationships, whereas with Graceling I felt that physical endurance came out more strongly? You're right when you say Fire is a quiet book, and I enjoyed the way that the past was so slowly revealed and how much Fire herself struggled with her own nature.

In both books I LOVED the feminist themes, and the very alternative (for fantasy) approach to fertility and children - Katsa DOES NOT want children, she is absolutely sure, and the man she loves says "fine, we can grow the birth control plants in our garden!" That has never happened in another book I have read. And Fire, although she wants children, refuses to do it, makes sure she never can, and embraces her found family! The most memorable parts for me, definitely.