The United Kingdom DVD release of Let The Right One In included an English commentary audio track with Tomas Alfredson and John Ajvide Lindqvist commenting on various things throughout the film. An srt file has been transcribed from the audio commentary (an srt file is a subtitle file that is compatible with many DVD playing programs, such as vlc). The srt file may be found here.

If you are interested in the commentary but don't have to time or inclination to actually play the DVD, below is a transcript created from the srt file.