Two thumbs up for a wonderful story! If you have a child that loves rocks, he will be able to relate to this story's character (who was the author's father). It's an opportunity to learn more about the Model T and The Great Depression as well.
Homeschooling families may be interested in the free literature-based unit study for this book at: http://www.homeschoolshare.com/rocks_in_his_head.htm . There are also free lapbook and notebook components for the book with the unit.