User blog comment:LuckyTimothy/Let Me In -- to satisfy the vampire needs..../@comment-168.18.240.1-20101005175240

It might have had low box office because of the over-saturation of vampires in our media -- film, tv, books, etc. And the possibility of an independent studio incapable of properly marketing the film. Though, I've seen quite a few commercials for the movie, so that might not be it.