The 2010 film Let Me in is an American remake of the Swedish vampire film Let the Right One. Directed by Matt Reeves, Let Me In tells the tale of a boy being bullied at school Owen (Kodi Smit-McPhee) and the friendship that developes between him and a feminine vampire Abby (Chloe Meretz). In the Sweedish film, the characters are Oskar (Kåre Hedebrant) and the vampire is Eli (Lina Leandersson).
Overall, the American remake is competently done and retains many of the qualities that made the Swedish version so beautifully frightening. However, it also features some rather shoddy special effects work. Furthermore, the two key relationships - those between the boy and his new vampire friend and the vampire and her guardian - are presented with less ambiguity than in the original. This is critical in the sense that it's clearer much earlier in the film what is really occurring plot wise, thus dissolving some potential tension.
Another big difference, is that Owen is less disturbed then Oskar. In Let the Right One In he is a potential serial killer or school shooter. We even see him collecting material on murders and serial killers in a scrapbook. In Let Me In, he's merely lonely and angry with being bullied.
Also of note, in the Swedish original, there's a brief shot, that suggests that Eli is not a girl, but rather a castrated boy - which follows from the back-story of the book by John Ajvide Lindqvist that the Swedish movie was based upon. However, in the American version, the shot is absent - although set up, which made me wonder if it might show up in some extended edition on DVD. Also, here in the American version, Abby is presented as much more feminine, whereas in the original, the presentation of her character was more androgynous.
With this change comes a fundamental shift of the dynamic of the two movies key relationship. In the American version, it's much, much more suggestive of a romantic relationship, whereas the original skewed more towards the main characters developing a very close friendship. Although, Abby keeps insisting (as in the original) "I'm not a girl".
One of the few upsides to the remake (besides the reduction of an annoying subplot about a woman who is turned into a vampire by Abby/Eli) is that Chloe Meretz gives an amazing performance as Abby, giving a subtle and mature performance as a hunted and ancient creature. Not that Lina Leandersson didn't give a strong performance, just that Meretz gives the more memorable one. None of the other actors in the American version, in my opinion, are better or worse, when compared to their counterparts.
With that said, if one has a choice, I would recommend the Swedish version over the American remake. Let the Right One In overall has better atmosphere and more interesting character development, with none of the embarrassing special effects work of Let Me In, thus making it a clear decision.