Shadow of Night, by Deborah Harkness

I'm still in the process of reading book two of this series.  I have to admit, I'm not loving it as much of the first one.  It seems to go on endlessly, but I am invested to see what happens in the end.  

Here is the publisher's summary:

The first novel introduced Diana Bishop, Oxford scholar and reluctant witch, and the handsome geneticist and vampire Matthew Clairmont; together they found themselves at the center of a supernatural battle over an enchanted manuscript known as Ashmole 782.

Now, picking up from A Discovery of Witches' cliffhanger ending,Shadow of Night plunges Diana and Matthew into Elizabethan London, a world of spies, subterfuge, and a coterie of Matthew's old friends, the mysterious School of Night that includes Christopher Marlowe and Walter Raleigh. Here, Diana must locate a witch to tutor her in magic, Matthew is forced to confront a past he thought he had put to rest, and the mystery of Ashmole 782 deepens.

Deborah Harkness has crafted a gripping journey through a world of alchemy, time travel, and magical discoveries, delivering one of the most hotly anticipated novels of the season