Ok, let's see what I have here...
'The Vampire Book - The Encyclopedia of the Undead' by J. Gordon Melton is excellent. Almost 900 pages long and full of great information. You can look up countries and learn about the type of vampire in that area. My favorite vampire reference book.
'Vampires - Encounters with the Undead', edited by David J. Skal is a collection of literature about vampires. It's interesting to see different takes on the vampire legend in the past couple of centuries. Another big book, almost 600 pages long.
'Vampires - A Field Guide to the Creatures That Stalk The Night' by Dr. Bob Curran is specifically about vampires in different parts of the world. The areas covered are
'Germany/Austria', 'Sumeria/Babylonia', 'Philippines', 'Puerto Rico/Mexico', 'Ireland', 'France/Scotland', 'Iceland', 'Hebrew', 'Wales', 'Brazil', 'Malaysia', 'India', 'Albania', 'Romania', 'South Africa', 'United States', and 'Greece'. Smaller book, just over 200 pages.
'Vampires - A Complete Guide to the World of the Undead' by Manuela Dunn Mascetti. This one is hard to categorize and much of the information is available elsewhere. But it's a good read and has many interesting pictures. Just over 200 pages.
'Vampires, Burial, and Death - Folklore and Reality' by Paul Barber. Supposedly offers the 'first scientific explanation for the origins of the vampire legends'. Gives quite a bit of information about burial customs in different parts of the world and what exactly happens to a body after death. Just over 200 pages.
'The Vampire in Europe - True Tales of the Undead' by Montague Summers. A collection of supposedly true accounts of real encounters with vampires. Originally published in the 1920's but there have been several reprints. Just over 300 pages
'The Science of Vampires' by Katherine Ramsland. A more 'scientific' look at all aspects of vampries. Unfortunately (IMHO), she lumps 'psychic' vampires (who steal 'life energy') in with 'real' vampires (who drink blood). Roughly 250 pages.
'in search of Dracula - a true history of Dracula and Vampire legends' by Raymond T. McNally and Radu Florescu. Another older book, originally published in 1972. This focuses exclusively on 'Dracula' as 'Vlad the Impaler'. Just over 200 pages.
Have fun reading!!