The Sorcerer's Stone Wrigte

The main story is the sorcerer's stone wrigte. And if you had asked me when that part of the book got started, i would have told you around 25%. But at half way through the book, they are just getting to hogwarts and going through the whole sorting hat. When i did that scene ofsorting the hat, i realized my thumb was almost to the middle of the book. And it was like, what in the world is going on?