Reading the book I felt once again drawn into Castle Rock (Needful Things being the final part of the Rock trilogy), and the plot was a variant on the "demon comes to small redneck village" type story King likes to tell. The characters were all described in loving detail, and it made both a good psychological and gory horror. The film on the other hand is awful. Gone are the character interactions and clever plot, and replaced by a story that tries to be exciting but misses by a mile. If you haven't read the book then you might enjoy this, else avoid at all costs, as with most films of King's books.
Review of Needful Things
