Paulsen, Gary. Soldier's Heart: The Story of the Enlistment and Due Service of the Boy Charley Goddard in the First Minnesotta Volunteers: A Novel of the Civil War. 1998.
This book should be popular for anyone looking for a short book. While the intended audience is middle school, a high school student interested in the subject matter would also enjoy it.
Charley joins up in the Civil War despite the fact that he is only 15. He is trained and shipped out to War. He sees many battles and amazingly manages to stay alive. The novel focuses on particular battles such as Bull Run and Gettysburg and explains them pretty well. After reading the novel, the reader should have a better understanding of the Civil War and what it was like to be in battle.
I recommend this book to anyone that enjoys historical fiction, particularly war stories. While many historical novels about war detail life at home, this one tells what life was like for the soldier fighting the war. While there is a good bit of death, the deaths are dealt with without any gory detail so readers will not feel uncomfortable reading it.