Gone Girl: the middle of the book is why you read it

I won't say what happens at the halfway point. If somebody has already told you, I'm sorry, and you should still read it for how she pulls it off.

Neither of these two people is likeable, and that's what kept me going. Every time I picked a side, the book made me feel stupid for it. The ending splits people. I hated it for a week and then decided it was the only ending that could have worked.