Gothic refers to a Romantic literary style which can include supernatural aspects, particularly vampires. This is because many of these stories are set in locales with Gothic architecture. This page includes significant non-fiction and fiction books about vampires and related subjects.
Gothic literature shouldn't be confused with texts in the Gothic language, the earliest written Germanic language, which includes the Codex Argentius, a translation of parts of the New Testament.
The Vampire, his Kith and Kin,
by Montague Summers. 
Summers, a devout and very literal Catholic, was apparently convinced of the reality of the undead. This work is a serious, often pedantic, academic review of the literature. However, it is required reading for any prospective vampire experts. (An Internet rumor has it that Buffy Summers got her last name from this author; we welcome any comments on whether there is any truth to this.) This etext was scanned at sacred-texts.
The Book of Were-Wolves,
by Sabine Baring-Gould. 
All killer, some filler. This is one of the best known studies of lycanthropy, written by the author of the hymn 'Onward Christian Soldiers.' The first ten chapters are a pretty good review of the shape-shifting literature, and then it takes a strange left turn into the topic of psychopathy. This etext was scanned at sacred-texts.
by Mary Wollstonecraft Shelley 
It's alive! This modern reworking of the Golem story is a cautionary tale about science. Frankenstein just keeps getting more relevant as we stumble forward into the 21st Century of clones, stem cells and genomics. Mary Wollstonecraft Shelley, along with her husband, the poet Percy Bysshe Shelley, was a member of Lord Byron's circle; her mother, Mary Wollstonecraft, wrote one of the key feminist documents, Vindication of the Rights Of Woman.
by John Polidori 
Originally spuriously attributed to Lord Byron, this was actually written by Dr. John William Polidori, a physician friend of Lord Byron. The main character of Ruthven is reputedly based on Byron. This short novel caused a sensation at the time, and spawned a vampire craze, with numerous books and plays based on or imitating its story line. For more information, refer to Chapter V of The Vampire, his Kith and Kin.
Lair of the White Worm by Bram Stoker . This novel, also by Bram Stoker, is an erotic thriller of demonic possession, this time by a giant invertebrate. It was made into a dreadful movie by Ken Russell, which has become something of a cult classic. Note that there are racist terms and characterizations in in this book, so be forewarned.
Vikram and The Vampire,
translated by Sir Richard R. Burton. 
This collection of Hindu fables, which has an Arabian Nights-style backstory with a legendary Indian monarch playing Scheherazade to an undead being, doesn't have much to do with vampires, but this seemed the best place to put it. Burton, as it happens, also translated the Arabian Nights.