Take a book where the two main characters are completely unlikable, vile human beings. One is a cad, and the other is completely psychotic.
That's Gone Girl, and it's a great book.
In Gone Bitch, Lookner goes one step farther to make every character unlikable. Amy is still as psycho as ever, and Nick is still a manwhore.
But it's actually hilarious, and you kind of
like Nick, because he's a "guy's guy".
It still follows the same format of jumping from character to character perspective, with the added bonus of one chapter from Amy's parents' point of view.
A fun quick read.