I would suggest:

1. Gods and Generals

2. The Killer Angels

3. The Last Full Measure


Those 3 books form a trilogy that tells the story of the military campaigns in the Civil War from beginning to end, and with plenty of coverage of the primary characters on both sides. That war was partially about slavery, partially about state's rights, partially about relative proportional representation in Congress, partially about rapidly developing industrialization (in the North) versus an old agrarian society (in the South)....very much about money (as usual)...and political power (as usual). The emotional issue to provide as a strong motivator for people in the North to go and fight was the slavery issue. People aren't so likely to go and fight over crass issues of who gets the money and political power...but they will fight over a moral issue like slavery, that's for sure.

There were both ethical issues and pragmatic issues. There were many good people and a few scoundrels on both sides. There was right and wrong on both sides. The side that was weaker in numbers and industrial strength inevitably lost after several years of bitter, absolutely terrible warfare, most of it fought on Southern ground. More Americans died in that war than in all the other wars the USA has fought.