Also interesting to me in terms of my own reader reactions to this book was my realization about halfway through that the genre tropes Harkness is working within are more tied to romance than fantasy. Which explained the female witch protagonist's constant fainting and passing out and needing to be carried about hither and yon by the male vampire love interest. That wouldn't fly in a strong female fantasy character, but it is a trope (or subtrope or something) of romance.
What I really did like about the book was that much of it was set at Oxford University, and the sense of scholarship and history in the book is very strong. Our heroine is a historian specializing in the traditions of alchemy, and Harkness really made me believe that in a big way. She acted like a historian, thought like one, talked like one. Harkness' own scholarship in writing the book was certainly deep enough to be utterly convincing to me. Her interweaving of history with the plot was fascinating.
This book was a lot of fun. It's the first third of a trilogy, so very little of the plot is resolved at the ending, but that's life. Worth the read.