Alright, I read this psychological thriller, its about a man who kidnaps his "sister" to try and figure out why she left when they were kids. He keeps her tied up in a barn and there's a storm outside. The cover artwork is a close up of a barn door with a hand on it. i'm pretty sure the title is only one word.

The sister is older, the Dad is gone all the time in the story and the Mom is a head case. They burn down a barn, and the girl keeps a journal written in her own secret code, she's a genius and the boy is a little mentally slow.

It turns out the man telling the story is a serial killer and the woman he's telling his story to is not his sister, his sister died along time ago, but he kidnaps woman tells them the story and then kills them, all the while believing they are his sister.

I'm trying so hard to find it, and have tried everything to find it, please help!