This book is really good! On the challenging scale, I would give it a 3 - just right! The summary is basically that there are these people, Ms Mauvias and Dr L. They are the bad guys. They basically go around and convince people to trust them and then they change their skin so that if they are like 100 or something, it would look like they are 20. In this book, they take a bunch of kids and force them into child labor making chocolate. They want this special chocolate to make them immortal. But then Cass, Max-Ernest, and Yo-Yoji stop them by telling the police and stuff. There is a lot more, but you know, SPOILERS!! I would recommend this book to 3rd - 7th grade.