*your mileage may vary
Chances are your library is seeing an uptick in interest for horror-related books and movies right now. Why not highlight your collection's hair-raising nonfiction alongside your well-loved Stephen King paperbacks and such cinema classics as Hocus Pocus?
Local histories may be the place to start. In my experience, there's a lot of supernatural-centric local lore out there; a personal favorite is Ghost Railroads of Indiana. But if your area is ghost-free (bummer!), read on (if you dare) for some scary search strategies...
**(When I worked at a public library, I pushed pretty hard for this to be our Halloween display's title one year. I was outvoted. The horror!)