Native Americans in the Lake Superior basin mined copper and traded it beyond the area. They directed white settlers to copper lodes and explained the mineral's significance and "wonderful power." This work examines the archaeological record to relate the story of this prehistoric industry.
Martin fills a number of pages with debunking other work, without adding much more to the body of knowledge. It's a refutation of the idea that ancient copper mines were worked in the Lake Superior Basin. Granted there are some wildly speculative books out there, but not enough to justify a whole book agin' the subject.