This summer will be the 150 year anniversary of the Battle of Gettysburg, one of the deadliest periods of the Civil War. The three days saw record causalities and is also considered one of the turning points of the war. Instead of breaking out a dusty nonfiction tome, consider The Killer Angels by Michael Shaara. This fiction book does a good job at adequately describing the events that did occur, but shines at getting into the heads of the major players. We meet Lee, Longstreet and Chamberlain and start to understand their thoughts, positions, opinions and fears as they prepare and head into battle. This is well researched, and really readable. The maps give you a good visual perspective as well.
One of the things I love most about history is not only learning the outcomes and the details of the events that took place, but investigating the other possibilities, thinking about the what-ifs, and figuring out the decisions that went into what really happened.