I kind of wish this had popped up right after Something Wicked This Way Comes because it is very thematically similar. I have read the book and seen the movie, the book has a slight advantage. As the final chapter in the three part "Castle Rock Trilogy" that was my gateway into Stephen King's writing, it certainly leaves the sleepy coastal town in Maine with nowhere else to go. If you are curious about the other two parts of trilogy they are The Dark Half and a story in Four Past Midnight called The Sun Dog.
Needful Things is the name of the antique store opened in Castle Rock by Leland Gaunt at the beginning of the story (he is played by Max Von Sydow in the movie). As customers are drawn in, he offers them their fondest wish in exchange for a harmless favor. In various Rube Goldberg or Final Destination type ways, these small favors create ripple effects that lead to real horror. Local Sheriff Alan Pangborn (Ed Harris in the movie) has to unravel the mystery behind the shop and Gaunt before his whole town is destroyed.
The ending of the book is one of those pure King endings that only works in your mind's eye and would look seriously goofy in the real world. If I recall, the movie changes the ending anyway. I would say either is worth checking out.