Gettysburg: A Novel of the Civil War
The story takes place in 1863 when Robert E. Lee and the Army of Northern Virginia are victorious at the Battle of Gettysburg instead of the United States. (Instead of attacking the Union line on July 2, 1863, Lee conducts a broad turning movement and forces the Army of the Potomac to attack him in a favorable position.) Gettysburg becomes something of a footnote in the main battle, which takes place at Union Mills in Maryland. The defeat at Union Mills is a grave setback to the United States, but it by no means spells the end of the war or determines its outcome, and the United States still has a lot of fight in it.
The Killer Angels
The Killer Angels (1974) is a historical novel by Michael Shaara that was awarded the Pulitzer Prize for Fiction in 1975. The book tells the story of the four days of the Battle of Gettysburg in the American Civil War: June 30, 1863, as the troops of both the Union and the Confederacy move into battle around the town of Gettysburg, Pennsylvania, and July 1, July 2, and July 3, when the battle was fought. The story is character-driven and told from the perspective of various protagonists. A film adaptation of the novel, titled "Gettysburg", was released in 1993.