The Historian by Elizabeth Kostova is one of my favorite books. It's got vampires and old books and Eastern Europe and libraries and the Hagia Sophia and finding in clues in ancient maps and descriptions of food and Vlad the Impaler and mysteries that are solved by historical research! What's not to love? I wish I would receive a tiny mysterious book that would send me off on a far-flung investigation through Eastern Europe! I will say that the ending is a little thin if you really think about it, but I still thoroughly enjoyed it. (I've read it three times.) It's like Indiana Jones, but with more emphasis on the history and less on the blood-thirsty natives.
Find it at your local library or on Amazon.