I think you are referring to the Sookie Stackhouse series by Charlaine Harris. I have not read this series and so am unable to comment on it. As for the popularity of vampires in fiction, there has long been an appreciation for horror in the arts (example) and it is not something that Christians must avoid at all costs. While individual works may or may not be appropriate, that does not mean that all works that include vampires are bad.
The archetypal vampire novel Dracula by Bram Stoker has long been considered to be, at least in part, an allegory with significant Christian themes and symbolism. Other vampire novels live in its long shadow (so to speak), but often depend on the Christian-based mythology it made popular.
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