I read this book in order to write up a reading/math lesson related to circumference. I thought that the book was very informative, had terrific pictures, and was a fairly easy read. I think that the children (6th graders) would enjoy reading it in class, if given the chance. I would have liked if the book went over, in more detail, how he determined the equation. (The children tend to ask how he got it!) It would have been useful to know the equation he used, but it does not matter because one's lesson can be modified to use the information provided in the book. I tied in the reading to a circumference lesson and had the children find the circumference of the earth.Overall, this is a terrific book. I thought that it was a fun read, and is a great teaser when going into a circumference lesson.