A Discovery of Witches, by Deborah Harkness

Wow. While not the best amalgam of history, fantasy, and romantic suspense, it's a pretty good story. We have a powerful witch who refuses to use her power, preferring to blend in with the human world, but that all ends when she 'draws' a coveted manuscript to her by accident. We have a powerful vampire who at first only wants the manuscript, then wants the witch herself. We have daemons--they are the eccentrics of the world, the savants.

And this is only the first book in a series. Wish I'd've known that when I picked it up.