I'm in two minds about this story.
On the one hand, it seems rather obvious that it's one of the massive influences on the whole vampire genre (or at least one of the earliest stories utilising a number of now-familiar elements of the vampire lore). And it's a fairly interesting tale, too; exciting and mysterious and creepy.
On the other hand, there were things about it that annoyed me. The main character's slowness, for example - okay, I get it, she did mention over and over again how she's so starved for companionship and not used to company and all that, and of course those were different times, but she seemed awfully slow to understand even once the poor old General had all but spelled out everything.
The ending also seemed rather rushed, not to mention that the General simply coming over and telling his story seemed, well, a tad convenient? Then again, I suppose that since it was clear quite early on that the General's ward had fallen victim to the same problems, it wasn't too contrived; at least he had a reason to come and tell his story, and a reason that had been worked into the plot earlier on.
All in all, an interesting little novella and certainly a worthwhile read for anyone interested in the traditions of vampire fiction, but not one I'd consider a literary (or genre) masterpiece.