Verdict:

I question the author’s understanding of bullies. The way this movie deals with bullies indicates that the writer was either bullied as a kid and was left very bitter about it or only read about bullying hastily in some external source.
Other than that, it is an enjoyable dark film but it is important not to go into it expecting a run-of-the-mill horror movie.
This film deals in subtlety. Arguably, it may not even be a horror movie in the modern sense of the word. Modern horror movies try to gross you out, create a strong tension and throw jump scares at you. There are no jump scares here. The macabre content is well distributed over the length of the film. The gore is infrequent, allowed to happen naturally and is not shoved in your face like it would be in a horror movie.
The film’s not scary but rather creepy and psychological, with the casual nature of violence, sexual undertones and psychopathic tendencies.
This movie is really more of a drama in a horror coating rather than a horror film. It is about the relationship between the main characters, and that relationship is very believable. The level at which the two young actors operate is quite impressive for their age. The movie is interesting due to its themes, such as loneliness, manipulation, innocence and lack thereof. Many of the themes present in vampire films are present here, but dealt with more subtlety and intelligence.
It should be noted that Let the Right One In is a slow burn and camera shots tend to hang for a while, centered on people’s faces with a narrow depth of field, up close and personal. When special effects are used, they are of mixed quality. There are a few really fake looking CGI cats in this film. Thankfully, the effects are not overused and are not that important.
This film feels like a fresh take on the vampire story. It lacks the Hollywood’s over-saturated pomp and feels far more natural, with the focus being on the relationships. It has psychological depth and comes off as both creepy and charming.