I’ve enjoyed several books this year (2015) that I would count among my favorites, but the one that’s left the deepest impression is Nigel Hamilton’s “The Mantle of Command,”which looks at a defining period in the life of President Franklin Roosevelt—the first year of World War II. Mr. Hamilton has created a masterpiece that is the counterpoint, in many ways, to Winston Churchill’s well-known “The Second World War” series, which painted a heroic portrait of the charismatic prime minister. FDR never had the chance to pen his own autobiographical account of the war, and history has sometimes portrayed him as something of a bystander to the war. Mr. Hamilton corrects this misperception, detailing Roosevelt’s wise tactics for slowly building up America’s military forces and showing how he had to go around the backs of his own advisers to ready the U.S. for its entrance into battle. What emerges is a portrait of Roosevelt not only as a truly great leader, but an excellent strategist and commander.