The US Civil War
The Bride of Texas by Josef Škvorecký: A look at Czech soldiers who fought in the American Civil War. I read this a long time ago, but I remember it being quite thorough.
The Velvet Shadow by Angela Elwell Hunt: This is a Christian novel about a young female doctor who disguises herself as a man to act as a medic in the Civil War.
World War I
The Good Solder Švejk by Jaroslav Hašek: A hilarious classic about bumbling soldier Švejk who is on the Austro-Hungarian side of WWI, but can't seem to do anything right.
All Quiet on the Western Front by Erich Maria Remarque: A poignant look at German soldiers in the first world war. Remarque shows how these young men were drawn into the army by patriotic fervor, only to see how truly horrible, and how mundane, war can be.
A Farewell to Arms by Ernest Hemingway: The experience of an American fighting for Italy during the war. I appreciated all the mundane details that were portrayed. So much of WWI in the media is about trench warfare, but here we see people having drinks, playing cards, and waiting around until there's something to do.
The Cowards by Josef Škvorecký: I included Škvorecký twice because I think he was a fantastic author. This one kind of cheats because the main characters aren't truly soldiers, but actually young men who join the fight against Germany as the Germans are retreating through their Czech town. The book was very controversial in socialist Czechoslovakia, as it portrayed the young men as more interested in girls and jazz than about patriotism. Fun fact: I once wrote a paper about this book and Škvorecký sent me a postcard thanking me for my thoughtful essay!
Catch-22 by Joseph Heller: I wrote in an earlier post that this book did not live up to my expectations, but that's only because I was told it was absolutely hilarious. I still found it to be an interesting look at the crazy lives of WWII pilots doing bombing raids on Italy. It really showed the element of the absurd in wartime.
For Whom the Bell Tolls by Ernest Hemingway: A look at rebels during the Spanish Civil War. Poignant and fascinating.
The Soldier, the Terrorist and the Donkey King by David Kitz: This book is about the crucifixion of Christ, but it's told from the point of view of a Roman soldier, so you see the Roman legions from his perspective.
I could only come up with nine books. Any suggestions for book number 10?