When John Muir died in 1914, the pre-eminent American naturalist, explorer, and conservationist had not yet written the second volume of his autobiography, in which he planned to cover his Yosemite years. Editors Robert Engberg and Donald Wesling have here provided a remedy. Their account begins in 1863, the year Muir left the University of Wisconsin for what he termed the "University of the Wilderness." Following an accident in 1867 that nearly left him blind, he vowed to turn from machines and continue to study nature. That led, in 1868, to his first visit to Yosemite Valley, where he began his glacier studies. Muir spent much time exploring the Yosemite region, Tuolumne, and both the southern and northern Sierras, publishing articles, and keeping extensive journals through 1875, when he began to write for the San Francisco Bulletin and expanded his travels to areas throughout the west. Mining a rich vein of sources-Muir's letters, journals, articles, and unpublished manuscripts, as well as selections drawn from biographical pieces written about Muir by people who met him in Yosemite in the early 1870s-Engberg and Wesling have assembled what they term a "composite autobiography," providing brief interpretive and transitional passages throughout the book. This work is especially valuable because it documents Muir's formative years, when he is maturing away from "conventional cultural paradigms of work and materialism toward new ways of thinking about nature and its impact on human development."