The author of the wildly popular ""Magic School Bus"" series introduces kids to their own bones, muscles, joints, digestive tract, lungs, heart, and nervous system. Each body part is described in a few sentences on a double spread, cheerily illustrated with active multiethnic children demonstrating the points made. Graphic headings (""Your Blood Is a Delivery Service""; ""Your Brain Is Your Control Center"") grab attention and help clarify what follows. Explanations are most complete for mechanical parts like muscles and joints; more complex processes like digestion are abbreviated, but accurate as far as they go. Children will especially enjoy a sequence of four see-through pages (skin, muscles and bones, heart and lungs, stomach and intestine--with ""Your Brain and Nerves"" on the opaque page that follows), though their usefulness is somewhat limited since some organs are omitted and labeling is scanty. Still, a great deal of clearly presented information, in a lighthearted format that's sure to appeal to kids.