This book begins by describing how scientists classify animals according to how they are alike and different, and goes on to list some of the defining characteristics that make fish fish.  It then takes a closer look at each characteristic with clear, labeled illustrations.  There were some unfamiliar fish mentioned in the text (clingfish, hagfish) that were not included in the illustrations, and though the book says it has a reinforced library binding, the finish on the cover doesn’t feel like it will stand up to much wear.  Includes scientific classification chart.