The Girl Next Door by Jack Ketchum
After losing their parents in a car accident, Meg and her sister Susan move in with their aunt and cousins next door to David. They've been through hell but it's nothing compared to what they're about to experience at the hands of those who are supposed to care.
A bit of a slow start but quickly picks up after the initial introduction to many of the characters. Reminded me of a Stephen King novel at first with all the kids and small-town neighborhood vibes. I found myself angry with the main character and others, of course, but I think that was probably the author's goal. Such a sad and frightening story-- because it could be so real.
Here's the blurb:
Suburbia. Shady, tree-lined streets, well-tended lawns and cozy homes. A nice, quiet place to grow up. Unless you are teenage Meg or her crippled sister, Susan. On a dead-end street, in the dark, damp basement of the Chandler house, Meg and Susan are left captive to the savage whims and rages of a distant aunt who is rapidly descending into madness. It is a madness that infects all three of her sons and finally the entire neighborhood. Only one troubled boy stands hesitantly between Meg and Susan and their cruel, torturous deaths. A boy with a very adult decision to make.