This is one of the best first hand accounts of the Civil War ever written, and by a confederate General no less:
Destruction and Reconstruction: Personal experiences of the late war: Civil War Classic Library
I have a book, I think it is titled “Lee’s Generals”. It was written not long after the war and is very readable. It also gives a different view than one usually gets.
To understand 20th Century warfare you must study the Battle of Stalingrad, the absolute deathstruggle of the worst of totalitarianism. Read “Life and Fate” by Vassily Grossman. He was a Red Army News reporter during the war and followed the Red Army all the way to Berlin. After the War the KGB attempted to confiscate all copies including typewriter ribbons of this book. This, because he was the first to equate Hitler and Stalin as co-equal Demons.
One of the main characters is a particle physicist; much of the book deals with his theories and how the Party Apparatus attempts to suppress him. It is chilling.