Those books are so great ! I think I loved "Harrow The Ninth" and "Nona the Ninth" even more than the first book. I can't wait for the fourth one to come out.
I'm currently reading "House of Niccolo" by Dorothy Dunnett. It's the prequel to one of my favourite series, the Lymond Chronicles.
It's set in 15th century Europe, Russia and middle East. It's great?.