Hmm, coincidence? My answers are also Stephan King books. Namely 'The Stand' and 'Salem's Lot'. Those are some intense stories! The movie of the Lot, however, was crud crud crud. Oh well, can't win em all.

Any medium can frighten, if the recipient is using their mind in the way the author/creator intended them to. I have had nightmares after watching my dear BF play certain video games! Books have had me jumpy for days (see the above titles). Even some artwork can invoke fear.