I also enjoyed this book. I saw a special on TV about Elizabeth Kostova, and I convinced my mother to get me the book for Christmas. I read it in, like, two or three days. I loved it.
I think I liked it mostly for the same reason I liked The Da Vinci Code--because I liked getting all the information the way it was given. Whether it's true or not, it keeps me interested and always going, "Wow, wow, wow." Having done a lot of research on Vlad Tepes (since I am a vampire fanatic), I can honestly say the information on him is pretty accurate. The only complaint I have is what I have with a lot of Tepes vampire stories: Vlad Tepes's nickname--Dracula--was the only inspiratoin from Tepes himself Stoker used. He had written the whole story where the Count had a different name, and after he had completed the story, he ran across the name "Dracula" in a book or something. He found out it meant "dragon" or "devil" and decided to replace the Count's name with it, and voila, we have Dracula.