The Mist (1980) novella

Stephen King's 1980 novella The Mist, originally published as a short story of the same title and later a 2007 movie, contains a far bleaker ending than what was depicted in the movie, though that too was pretty horrific. The movie pretty well follows the novella up until the point at which the group of characters including the "hero", David Drayton, leave the supermarket to try and escape. The impression you are left with in the novella is that The Mist has enveloped all of Massachusetts and possibly even more of the New England states so that the end of the world may very well be at hand. The Mist is in many ways a precursor to Stephen King's epic novel Under the Dome (2009), except in the latter there are no extra-dimensional monsters. Quoting Stephen King, the Wikipedia entry on Under the Dome notes that the novel "concerns itself with how people behave when they are cut off from the society they've always belonged to." This is exactly what happens in both the novella and movie versions of The Mist.