Ruth is one of the best villains I've seen. Evil. Heartless. Makes her children hate women because she hates women and herself. Gets her boys to drink alcohol because she's a drinker and doesnt want to drink alone. She teaches sadism and power trips to kids and speaks on their level to communicate the evil. It's truly messed up. Nothing short of torture. It's not just shock, the character of Ruth says some interesting psycologically revealing things. It just adds to the darkness.
It did feel tiresome near the end as Ruth's manipulative wasn't a bigger part because the character of David didn't really shine when he needed to. It became torture without a motive. David never had much of a personal journey. I didnt feel his pain. He didn't react to the torture in interesting or natural enough ways. The movie doesn't have much replay value as a result but it's worth a watch.

Based o a true story? Maybe it should have told us that unless I missed it.

I don't understand the negative reviews because of the shocking content. If you want horror then this is horrific. It's no cosy Stephen King adaptation.