Wow, I have to say I was really surprised by this movie. That being said, I haven't read Stephen King's novella and I didn't know much about the story going in beforehand, but for some reason I had a feeling that I wasn't going to like the film. I don't think the trailer did it any justice, because I was wrong.
The thing is, I don't really have a thing for monster movies - I don't dislike them, but the vast majority of them (in my opinion) have been moronic with no redeeming value whatsoever. However, this isn't really a monster movie, at least not in the sense that we think of when we use that label. I think it's really about the capacity we have as humans to act like monsters rather than what is outside the supermarket. Don't get me wrong - I quite liked the monsters (those spider things were fucking creepy), but Mrs. Carmody (Marcia Gay Harden) screaming "We want the boy!" was one of the best scenes of the film, particularly because of what happens towards the end of it (you'll know what I mean if you ever see this). And I'm going to go off on a tangent and just say that the old lady ROCKED. She had some of the best lines/moments.
The ending really does just wrap the entire film in a big shocking, violent and honestly surprising bow. I had a feeling something like that was going to happen, but I didn't quite realize just how good it would be. The earlier scene where the father makes a promise to the son clued me in that something was going to go down. You don't see too many endings like that and I really thought it was fantastic. I do think one of the guys who reviewed it over at Bloody Disgusting was correct when he noted that the ending will make or break the movie for you. Some will like it, some will absolutely hate it.
There are a couple of things that did not work for me. The first, and most important, was how it seemed to slow down quite a lot in the middle of the movie. I understand some lulls, but this one seemed to go on and on. I thought the scene leading up to the sacrifice took too long and honestly, I was a little bored. And finally, more minor but still genuinely distracting, the music at the end was used way too much and I didn't think it was an appropriate match in the first place. That could be because of the lack of music prior to its use (which was good), but it did seem out of place to me. A soft score might have worked better, rather than forcing some sad song down our throats. I'm aware the moment is sad, I don't need Arabic women wailing (I'm guessing it was Arabic, but it was definitely wailing of some sort) at me for me to understand that fact.
Notice how I am not saying what the ending is. Stephen King said that anyone who revealed it should be hung until dead, so I'm taking that threat seriously. He's kind of a scary (but cool) guy. I have a crush on him and those glasses of his, so I obey.