Investigators know that if they interview ten witnesses to an event they are likely to get ten different reports. Figuring out what really happened requires sifting through the data and finding the agreements, determining who are the most credible witnesses, etc. To arrive at an accurate picture of an event is not so easy as evaluating one testimony or one photograph and extrapolating from that to the big picture. That's how dishonest historians evaluate the past. Honest historians study the big picture.
And that's how it is with understanding the Civil War, or as one book is titled, The War Between the States: America's Uncivil War
by John J. Dwyer and other contributors.
A broad and deep study is necessary. I've just begun the book, but I'm already impressed by the author's approach and common sense. He speaks of the war as a "Fifty Years' War" that involved numerous factors: economic, religious, regional. Slavery was one issue among many, a factor yes, but not necessarily the most fundamental.
I found this in the introduction particularly interesting: