My Vicksburg — Ann Rinaldi

Claire Louise Corbett and her Confederate family flee their home as Union soldiers shell their town of Vicksburg, Mississippi. They venture out from the safety of a cave only three times a day, when the Union army takes their meals at eight in the morning, noon, and eight at night. Although many of the townspeople suffer from a lack of food, the Corbetts receive extra rations from Claire Louise's brother, Landon, a doctor with the Union army. When Claire Louise discovers her brother tending to a Confederate soldier who is responsible for Robert E. Lee's "lost order" (causing the South to lose the Battle of Antietam), she is forced to make a difficult choice between family and friends.
Award-winning historical novelist Ann Rinaldi paints a story of family, courage, and secrets during the forty-seven-day siege of Vicksburg, a battle that has sometimes been ignored in history because it ended the same day as the Battle of Gettysburg.