Hassler s history will survive as our most detailed narrative of the first day s battle, examining the day s action so minutely that no succeeding historian of Gettysburg will be able to ignore it. Hassler s book has solid virtues in addition to its thoroughness of detail: it offers a persuasive argument that the first day s events largely determined the eventual outcome of the battle; Hassler displays uncommonly complete knowledge of the battlefield terrain and] makes uniquely good use of the information that can be gleaned from the monuments and markers on the battlefield. American...