[The Electromagnetic Spectrum: Key to the Universe is a] fine summary of the history of observation and reasoning which led to our present understanding of the phenomenon by which we see, communicate over long distances, and investigate both the largest and smallest parts of the universe. Mr. Branley nicely covers the connection between electricity and magnetism investigated by Faraday, the theoretical handling of that relationship worked out by James Clerk Maxwell, and even the rather difficult concept of radiation as being both wave and particle at the same time. The ways in which the behavior of radiation helped elucidate the structure of the atom is clearly explained, allowing for the nonmathematical treatment required by the intended audience and the consequent need to depend on analogy. Even the practical uses which follow from the properties and behavior of the various wavelengths of "light" are well covered.