This book does a good job (as I have found to generally be the case with this series) of taking some pretty complex scientific concepts, such as friction, inertia, and centrifical force, and explain them in clear and understandable language.  It sets up several experiments to illustrate its points that students could fairly easily replicate on their own.  In addition to the experiments for students, it also includes information about famous scientists and the early discoveries regarding motion.  I do however have one and a half gripes: gripe number one is that when it is describing the effects of centrifugal force, it never actually names it as such, missing a perfect opportunity to build scientific vocabulary; my half gripe is that it sets up experiments for students to conduct, and then proceeds to describe what the results would be, thereby taking away the need for students to actually try it themselves (but it’s only half a gripe, because I grudgingly acknowledge that this way students who wouldn’t bother to do the experiments may actually learn from them anyway).