Quick-take: I really wanted to like this book, but it had too many essays and not enough Dracula.
This book is presented as a series of diary entries, letters, and other correspondence. I find this a decent story mechanic if used with caution. I suppose it makes the "action" feel more real, but it makes it really hard for me to get absorbed or feel any tension.
Because it is a journal entry, everything that is being described has already happened.
Dr. Seward's Journal. Aug 20 I examined Lucy. She seems to sleep many hours..."
It is interesting because I am placed in the middle of their anguish. However, it is just too quirky. They are talking about the past while living in the present. Then the next chapter moves the date forward. Now, we are reading about the past again but several weeks later.
Personally, I would have preferred a standard linear timeline. The mental calculation of what time we are at and how much we just shifted forward is a story mechanic I could simply do without or at least used sparingly. The entire book is written this way.
My other problem with this book: Not enough Dracula. I was introduced to the super-creepy Count Dracula near the beginning of the book. He is buying an estate in London. It was interesting reading about late 19th-century real estate logistics. Anyway, Dracula is pushed to the side after a few cool chapters. Then we have a long, long slog of Lucy becoming ill, writing letters to Mina, and Dr. Van Helsing investigating. Then Madam Mina falls ill and we learn about her sleeping a lot. This is 80% of the book.
Seriously, just let them die and lets get back to Dracula. If this book was not so famous, I would have given up pretty early. I kept waiting for it to get good, and I was rewarded for my patience with a fairly anticlimactic final scene.
I would not recommend this book unless you are interested in the origins of a famous fictional character.