I first read The Mist (as a short story in Skeleton Crew) when I was in 7th grade or so, and it's always been my favorite Stephen King story. I've been wanting them to make it into a movie for years, so this movie had a lot to live up to. I'm glad to say that, for the most part, it matched (but didn't exceed) my expectations. The movie plays out on the screen almost exactly as it played out in my head. Even though I haven't re-read the story in a couple of years, I knew who some characters were right away from their first appearance, just by the way they looked. I don't know if that's a compliment to the casting director, or wardrobe, or even King's writing for being so easily interpreted.
The movie follows the book very closely (except for the ending, which I'll get to in a bit). You know, I think the story is the perfect length to make into a movie: they didn't have to cut much out (other than the ending, I can only remember one scene in the book that wasn't in the movie, and I bet it was filmed), and they didn't have to add much in. Even without the story fresh in my mind, I generally knew what was going to happen next. Because the movie is set in a somewhat rural area, even the setting hasn't changed much since the story was written. The movie could easily have taken place 20 years ago, except for one scene where someone uses a cell phone as a flashlight.
Some of the acting is a little flat, and the whole movie has a little bit of a "made for the Sci-Fi Channel" feel to it, but I'm okay with that. I do wish they'd had a slightly bigger budget, as some of the computer FX could have used a little polish. But that's just the jaded FX cynic in me; if this had come out a few years ago, we would have been amazed. A warning to the easily grossed-out: The Mist does contain a few very good gore effects, some of which made me cringe. KJ had to cover her eyes through some of the bloodier moments, and even complained of nausea at one point.
The monster designs are very cool, and the director really understood the spirit of the story - knowing what NOT to show being more important than what to show. This movie is everything I wished the "Silent Hill" movie had been. My favorite thing about the SH video game was how it felt like I was playing through The Mist short story, and now The Mist movie feels like a better film adaptation of the game than the actual SH movie. One thing I didn't like: If I remember correctly, in the book, the characters put forth a lot of theories about what happened up at the military base ("Project Arrowhead") that caused the mist and everything in it. But they're never really certain, and that adds to the mysteriousness of it all. The movie, on the other hand, has a scene that completely spells out what caused the mist. Sometimes it's just cooler to live with the mystery. It's as if someone said that the Force in Star Wars was caused by microscopic bacteria in a Jedi's blood cells. Or if the immortals in Highlander turned out to be space aliens. I mean, really, who would do that?
The ending... Ohhhhh, the ending... I'm not going to spell it out exactly, but if you want to stay spoiler-free, skip this paragraph. In a word, the ending is cruel. It has an ironic "Outer Limits"-style twist, or at least it tries to. Instead it comes off like the punchline to a sick practical joke. Remember that part in the Bible, where God tells Abraham to sacrifice his son Isaac, and at the last moment an angel yells out, "April Fool!" (And people say God doesn't have a sense of humor.) Okay, now imagine the same joke if the angel had shown up a few minutes later. "Just kidding! You didn't really have to do that! Here, I'll help you clean up..." I realize the book's ambiguous ending wouldn't have translated well to the big screen, but I can think of a few alternatives that would have worked, IMO.
To sum up, I really enjoyed the movie. My favorite Stephen King short story turns into one of my favorite SK movies. I just hope the DVD has some alternate endings.