Promising review: "The book layout, the durability of the non-Lego paper components, the directions on how to fold the paper components, etc., are thoughtfully done. I supported my 7-year-old grandson's effort to build the first project. HIs greatest joy (and it was great joy) was the moment that first project functioned properly after several complete and partial failures. Then again once the chain reaction was easily repeatable so he could show his parents. After having some success he was excited about doing more projects. This is radically different than just sticking Lego pieces together and it's not easy. It's elementary physics of motion, weight, angle, momentum, etc. It appears that these complicated chain reactions are fun for children to assemble, challenging to make fully, reliably functional, and thrilling once they work for that first time. It's all good stuff!" —tenor1
Get it from Amazon for $18.37. If you want to complete the gift, add on some Legos!