Six years ago, Edward Snowden leaked a trove of secret documents about how the United States had built a massive surveillance apparatus to spy on Americans and people across the globe. Snowden was then charged in the U.S. for violating the Espionage Act and other laws. As he attempted to flee to Latin America, Snowden became stranded in Russia after the U.S. revoked his passport. He has lived in Moscow ever since. Snowden just published his memoir, “Permanent Record,” in which he writes about what led him to risk his life to expose the U.S. government’s system of mass surveillance.