I've heard the American remake, Let Me In, is almost identical. I haven't seen it. I have seen the trailers and they make it look like a horror film. I would not call Let the Right One In a horror film. There's no slasher element, no copious amounts of gore. Don't get me wrong, there are some moments of horror and some moments of blood, but if you wanted me to place this in a genre, I would say it's a coming of age tale. Coming of age tales are my fave. And this one is brilliant.
From a plot perspective, it's subtle and seductive. It doesn't explain anything - it makes us watch - and I adore that about this film. It has the most creative ways of revealing the rules of being a vampire that I've ever come across. And it stands up to multiple viewings; always engaging, always entertaining.
I recommend this movie most ardently. It's foreign - don't forget that. It has its foreign sensibilities. But it's worth the languid pace, I promise.