A tightly-packed compendium of general information about the variety and characteristics of America's mountains--somewhat arid in presentation. Sentences like ""The Green Mountains have many historical and recreational features,"" won't encourage you to whip out a piton. However there is a mass of solid material concerning the mountains' origins and the changing formations since they were tossed up millions of years ago. Costello discusses the various exposures, altitudes and climates which influence the incidence and adaptations of flora and fauna on the heights; the importance and uses of water; and what birds, mammals and lesser animals and insects to look for on the trail; etc. There is a chapter on the contemporary as well as past reciprocity between men and mountains (rather skimpy), and an appendix offers some tactics for mountain hikers.