In his Second Inaugural Address, delivered as the nation was in the throes of the Civil War, Abraham Lincoln proclaimed that both sides "read the same Bible and pray to the same God, and each invokes His aid against the other." He wasn't speaking metaphorically: the Bible was frequently wielded as a weapon in support of both North and South. As James P. Byrd reveals in this insightful narrative, no book was more important to the Civil War than...