What follows is a brief comparison of the novel Let The Right One In by John Ajvide Lindqvist, with the original Swedish film adaptation Let The Right One In directed by Tomas Alfredson, and the American film Let Me In directed by Matt Reeves. There are some spoilers below, so be warned.
I've had a chance to see both films as well as read the novel that inspired the original movie. I liked them all. There are some differences in the plot with the American version having a more condensed, tighter story that utilizes fewer characters. The important events remain similar enough and the emotional content has largely the same impact. But the American version is a remake of the Swedish film, not a reinterpretation of the novel that the Swedish film is based on, which I mean as an observation not a complaint.
For example, in the American film the old man who cares for the vampire is clearly indicated to be a former little boy that the vampire befriended years ago. That is definitely not the case in the novel where the old man was pedophile that was "adopted" by the vampire just a few years before the story. The Swedish movie could be interpreted either way. The book also makes the back story and sex of the vampire explicitly clear. The Swedish movie gives less back story but still provides strong clues that the vampire is a mutilated boy. The American version retains the line by the vampire saying that he/she isn't a girl, but that is it.
The little girl actress in the Swedish version portrayed a much more creepy, inhuman, and isolated character than the little girl actress in the American version who came across as much more vulnerable and sweet. But overall the American version had better acting, even taking the subtitles of the Swedish version into account. It certainly had much better special effects. But I was pleased to see that the style of the cinematography used in the American version paid some homage to that used in the original film. Despite the differences, the overall mood carries through the various versions of the story.
Thumbs up for all three versions.