I’ve liked Charles Mann’s earlier books as well as The River of Doubt, Turn Right at Machu Picchu, and Lost City of Z, and we do a good job hand-selling all of them. But none have had the impact of Scott Wallace’s The Unconquered: In Search of the Amazon’s Last Uncontacted Tribes (Crown, Oct.). If ever a nonfiction title demanded film treatment, this is it. The title at first seemed to refer to the Flechieros, the tribe that Wallace is tracking, but as he takes the reader deeper into the story and farther from his world, we start to lose certainty about much more than the book’s title. Many other provocative questions appear. Is Sydney a humanitarian hero or a misguided megalomaniac? A caring manager of the expedition’s safety or a petty dictator? At the end of the day, is he right or wrong? But what makes the book so utterly compelling is much more immediate: will the expedition avoid catastrophe? Wallace is to be commended for developing a tension and pace that kept me rapidly flipping the pages; I bet readers will feel the same way.