Interest in the Precambrian geology of the Great Lakes Region has been growing as documented by a new generation of multi-authored books. Two have been published recently: the volume under review and a companion volume, Geology and Tectonics of the Lake Superior Basin, Mem. 156. The Minnesota Geological Survey has published a regional Precambrian geological map at a scale of 1:1,000,000, and in 2 years' time newer data will appear in a DNAG (Decade of North American Geology) volume on the Precambrian of the conterminous United States. Thus, the papers in the volume under review provide a comprehensive view of the status of geological knowledge as it existed in the spring of 1981.