Shadow of Night begins immediately where A Discovery of Witches ends as we find out that Diana and Matthew have successfully time-walked back to sixteenth-century Elizabethan England on the night of All Saints' Day. In travelling back in time, our main lead characters expect to, first, make contact with a powerful witch who would be willing to teach Diana how to use her witch's powers, second, locate and steal the mysterious alchemical manuscript (Ashmole 782), and, third, protect themselves from the Congregation's clutches (waiting for them in the present/21st century).
I have had several issues while reading Shadow of Night the first one being with how the time travel was used and explained in the first few chapters of this book. It seems to me that the author thought that Diana's time-walking abilities should be created and used not because it made sense for the character's evolution but rather because, Deborah Harkness, needed a plot device to transform her romance fantasy novel into what she had been wanting to do from the beginning: a historical fiction. Also, I wasn't convinced about how the author described the actions and consequences of time-walking. It was too easy to have 16th century Matthew disappear and be replaced by 21st century Matthew pretending to be his 16th century self. But I can understand that the author did not want to deal with such a constraint and chose the easy way out.
However, there are certain elements in this book two of the All Souls trilogy that I cannot overlook. These elements are related to the plot of Shadow of Night that was promised at the end of A Discovery of Witches. This plot was simple and direct enough: go back in time, find a witch to train Diana, and retrieve Ashmole 782. Unfortunately, Deborah Harkness goes back on her promise several times throughout the book progression as she much prefers writing about Matthew and Diana's conflictual relationship as husband and wife, creating drama between and around them, and spending too much time talking about Queen Elizabeth I's rotten teeth instead of focusing on Diana and Matthew's real purpose. That is why it takes more than three hundred pages for the Bishop witch to find someone willing to teach her and yet, as soon as she does, the training is rapidly over making Diana the most powerful witch in all the history of witches without it being earned at all. As for the search for Ashmole 782, it takes even longer for the main characters to start looking for it and investigate its whereabouts simply because, despite what Deborah Harkness wants to make us believe, Matthew is not a great spy at all. Quite the contrary. We are told several times that Matthew is the Queen's best spy as he is good at getting information from people but, in the end, he fails everyone every chance he gets. This, in my opinion, considerably impacted the pacing of the story.
Moreover, there is another decision from Deborah Harkness that I did not understand and which, I believe, also contributed to affect both the plot and the pacing of the story. When I finished A Discovery of Witches and picked up Shadow of Night, I thought that the author would show us two timelines: the sixteenth century and present days (twenty-first century). Instead, we only have six chapters throughout the book which takes place in present days and none of these chapters actually shows how Diana's aunts and Matthew's family deal with the Congregation in the couple's absence. Luckily for our two main characters, the Congregation seems to be so busy with administrative paperwork and voting motions that they don't have the time to spy and investigate on the Bishop and de Clermont families except at the very end of the book, which to me, was another proof that Deborah Harkness should have spend more time showing the intrigue and plotting on the Congregation side as well as on the Bishop & de Clermont families.
Shadow of Night is a long, slow and boring book in which you never get to see how truly powerful witches can be or how terrifying vampires truly are. You will hear about witches and vampires' accomplishments but you will never be able to see it because Shadow of Night is all about telling but not showing.
Harkness, D., Shadow of Night, London, Headline Publishing Group, 2012.