My friend and I enjoyed this very much. It's true, not a big storyline, but the gore makes up for it. That's why I like Eli Roth's movies.
And as for the comments I've read. If you think movies like this are so twisted and horrifying, then why would you even try watching? If you rent it and watch it, don't blame your disgust on the movie. That's ridiculous. Maybe you should actually look at the cover and read the description and rating warnings on the back of it before watching it. Especially the quote from Stephen King.
And library isn't just for people looking for 'educational' there are morbid books in there too that have been around before they even started renting out dvds.