“The Man with the Poison Gun: A Cold War Spy Story,” by Serhii Plokhy. New York: Basic Books, 2016. 355 pp. ISBN: 978-0-465-03590-8, approximately $25 hardcover, $19 e-book, $25-$30 audio. Serhii Plokhy, one of the foremost historians of the former Soviet Union, has penned a nonfiction spy thriller. Dr. Plokhy’s latest book, “The Man with...