Mielczarek (physics, George Mason U.) and science writer McGrayne explore the critical importance of the metal element in life from bacteria to humans. They report on recent discoveries about iron and magnetism in bacteria, in myriad animal and plant species, and in humans, such as that many migrating animals have minute deposits of magnetite inside them that are sensory navigators. They also, of course, discuss the role of iron in mammalian blood and the iron-related diseases of humans. Annotation c. Book News, Inc., Portland, OR (booknews.com)