Ok this is the craziest thriller I've read in awhile! The twins in here are nuts and obsessive! Summer is obsessed with having it all and she does. Iris is obsessed with having all Summer has.... And more.
Their dad has a crazy will stipulation. It makes everyone willing to do whatever they can to get what the will can give them.

I think this one is a really good one to not know a lot about before reading but pick it up! It's insane and crazy good! I had to read the last two chapters twice to make sure I knew what happened!!