Tapper is also the author of The Outpost: An Untold Story of American Valor, a critically acclaimed book about U.S. troops in Afghanistan that debuted at number 10 on The New York Times bestseller list for hardback non-fiction. Bob Woodward described the book as "Brilliant, dedicated reporting by a journalist who goes to ground to get the truth. A sad, real tale about this war, America and the brave warriors who live—and die—at the point of the spear" and Jon Krakauer called it "a mind-boggling, all-too-true story of heroism, hubris, failed strategy, and heartbreaking sacrifice.