Whenever I'm trying to decide whether to give a book 4 stars or 5, I think, "Is this as good as To Kill a Mockingbird?" I think The Post-Birthday World isn't quite as good as that, but it's darned close. It's like an emotionally mature "choose your own adventure" book in which we get to see how the course of our life sometimes hinges on one decision. Shriver suggests that, in the end, the lessons we learn are the same, regardless of how we get there.