George B. McClellan

Stephen W. Sears examines George B. McClellan, who by 35 commanded all the Northern armies in the Civil War and was nicknamed the Young Napoleon. McClellan turned the Army of the Potomac into a fighting force to be feared and led the era's largest and longest campaign as well as the bloodiest single battle in American history, yet he let two chances to end the war decisively slip away. Sears also follows him into politics, when he ran against Abraham Lincoln as the Democratic presidential candidate in 1864. Written as neither indictment nor apologia, the biography rests entirely on primary sources and portrays a charismatic, controversial general who held the Union's fate for the first eighteen months of the war.

Ryan Holiday recommended it in his list of the very best books he read in 2015.