What do you think of this book idea?

The story sounds like one of those perfect families that get suddenly warped after something happens but then I lost interest when the twelve year old starts to investigate. And the father is the biggest victim so why is he out of the picture??? if it's written well and depicted in a mature manner the initial concept could be grown into something that would be as well like as it would be hated but if you don't know how to handle it it could just become porn. So my suggestion is to be very careful with it and if it's your first shot at mature and dramatic writing then drop it. Coz it could be a potential disaster