NOTE: Lost reading this book, or about to start reading it? Go to the back of the book and find "Libri Persona: The People of the Book" (I believe it is on page 579-581 out of 584 pages). It has a list of the characters and a brief description for each character broken down into the sections of the book. Bookmark it! It will help you out immensely considering all the different people and details in this book.
Shadow of Night picks up where A Discovery of Witches left off. Diana and Matthew go back in time to Elizabethan London in search of Ashmole 782. Though Diana knows about the Elizabethan age, she finds it hard to act the part. Matthew and his buddies try to help Diana by tutoring her in how to live in the 1590s. The story is detail rich, so be prepared to know a lot more about Elizabethan London by the end of the book.
While in the past, Matthew and Diana are faced with several quests. The first, to find Ashmole 782 and discover its secrets. The second, to find a witch to teach Diana how to use her magic. Both are extremely important in the book, but there is another important part. Shadow of Night gives a lot more details on who Matthew really is. You can easily see how much he has grown compared to his past self. You also find out how he interacts with his friends and family and why he is the way he is. This brings great new details to the series, since I felt that A Discovery of Witches didn't give very many details on Matthew.
Though I think the book was a great addition to the series, I found myself frustrated with preconceived notions on time travel. Yes, I have watched too many time travel movies / read too many books. Matthew and Diana seem to not be afraid to alter the past, and do not seem to worry about the ramifications that could happen. To each their own, it did take a little bit of my enjoyment away from reading. All in all, I suggest this series if you loved the first book.
Disclosure: I received a free copy of this book via NetGalley for an honest review.