The setting is really exciting.
The characters are extremely well done and one finds oneself really getting to know them and fear for their fate as the novel progresses.
There is also a lot of really intelligent discourse between characters in the book and a lot of it is highly relevant to modern society. That may be what I am enjoying the most. Modern elements viewed from the "safety" of the distant past. As one reads some of the conflicts about religion, women's (and minority) rights and notions on acceptance and/or blind hatred, one can see how the lessons in Flight of the Sorceress can be applied to life in 2011.
I picked this book up to better explore Britain in 400AD. I have found a meticulously researched historical fiction novel that is both captivating and thought provoking.