Gettysburg: The Last Invasion by Allen C. Guelzo.
Allen C. Guelzo examines Gettysburg through the experiences of soldiers and the practical realities of nineteenth-century combat. Command decisions, officer politics and the workings of army life become part of the battle's explanation.
Read it for how changes in scale alter historical understanding. The book invites comparison between a strategic account of a battle and the many partial experiences through which that battle was actually fought.
