The Girl Next Door suffers from a boatload of problems, from the very premise which is exciting if you thought Hostel 2 was too classy to the acting which is good if you've never actually met and conversed with live people. This movie is rotten from foundation to rafters, and suffers a series of huge gaps in logic and development, both of which are highly necessary to establish that any of the monstrous caricatures we're forced to watch are anything more than someone's paper-thin excuse for getting their kicks out at 24 frames a second.
I know, I know, it's based on a book, so therefore it's somehow loftier than Captivity or Turistas, but those movies actually had something in the way of set design and ambition to set them apart, rotten as they are. The Girl Next Door gives us hasty sketches of a monstrous mother figure who you've no choice but to hate from the word go, kids who fall into a lockstep of torture and abuse for no discernible reason and a washout main character who might as well be wallpaper-colored for all the impact he has as a narrator or character.
The setup is brief before the torture porn starts, and from there it's a freefall of implausibility. One day they're fighting in a bedroom, the next they've got a girl bound in the basement, tearing her clothes off, the next they're engaged in kiddie rape, while the Cruella DeVille mom urges things on. Neighborhood kids file in and out, never bothering to mention anything going on to their parents, the main character only seems to get around to caring about what's going on in the last 20 minutes and everything wraps up in a nice neat little bow, complete with a movie-of-the-week moral moment tacked on.
I could be snide and say the only good thing about this movie was how short it was, but there is no saving grace to this film. It's just plain ugly. If that's what you're hungry for, by all means, but if you actually enjoy horror films and don't utterly despise every other person on the planet, there are far better options on the shelf.