The Annotated Carmilla
Carmilla by Joseph Sheridan Le Fanu is one of my favorite vampire stories. Published fully a quarter century prior to Dracula, it influenced the latter and in fact all subsequent vampire fiction.
Here was the first story from a victim's perspective, a victim who believes the vampire a beloved friend, and experiences the feeding as a kind of not-quite-erotic dream. The prototype of Van Helsing makes his appearance, literature's first professional vampire hunter. Likewise this was the first real lesbian vampire (or so it has seemed to the vast majority of readers since then).
Years ago, I had the vast good fortune to receive The New Annotated Dracula as a birthday gift. I recommend it highly. Ultimately, its possession led me to begin doing precisely the same to Carmilla. At the time of this writing, over 350 footnotes dot the text.
Where, for example, is Styria where the story takes place? The narrator speaks of "traces" regarding a horse carriage--what does that mean? When exactly does this story happen?