Read Raphael Semmes book about the CSS Alabama .
The first 100 pages he spends on causes of the war, mostly taxation of the prosperous South being used to finance the struggling North, slavery was just a minor symptom of the argument over States Rights.
The war of the 10th Amendment .
Don't bad mouth Custer, he was a lot better cavalry commander than he gets credit for.
"a cavalryman with Custer" by JH Kidd is free on internet archive.