Grade 2-3–Clark has done a fine job of including meaningful content in a limited space. Each title consists of 10 two-page chapters printed in a font of an inviting size. Full-page photos–all color except one vintage photograph–with informative captions face two-paragraph text blocks. Planes features one of the best explanations of aerodynamics seen in this genre at this level, and Cars and Motorcycles achieve the same when discussing the internal combustion engine. Vocabulary is appropriate, even using the word traction when necessary, whereas most current series prefer to use the word grip instead. Brief mention is made of how manufacturers of each kind of vehicle are attempting to improve the environment by becoming greener.
