Only ambiguously a genre work, and rather atypical for King in that it's not definitely established that anything more fantastical than a dog with rabies happens in the novel. It’s foreshadowed pretty heavily what will happen--a dog receives rabies, goes nuts, kills some people and creates tension for others before being stopped--and that is exactly what happens. There’s some suggestion that the dog might also be possessed by the ghost of a local serial killer, but if so it doesn’t do much to the story beyond amplifying the creepiness factor at a few points, and is surprisingly less integrated to the plot than one would expect.
As the main device for a horror story, it works up to a point. Unlike a Lovecraftian horror jumping out of the sewers in the form of a clown, this layout is a lot more conventional and plausible, and gets some mileage from the sort of everyday menace of a very gentle dog being turned into a completely focused killer. There are some very engaging moments, and in particular the moment where the animal turns completely hostile for the first time is well done. The story goes on for too long, though, and by the time we’re in a multiple day standoff with people trapped in a car by the dog something of King’s usual urgency has been lost.
The wider backdrop is interesting, Castle Rock making for a vivid and well constructed environment. There are also some interesting reflections on advertising and marriage, and the ending has a ruthlessness that's disturbing. Still, in the end too much of the story is a flat stand-off with a crazy dog, which has limited possibilities for sustained drama or horror.
Worse than: The Shining by Stephen King
Better than: Song of Sussanah by Stephen King