I'm convinced that the failure of reconstruction explains the current state of US politics, perhaps better than an analysis of the civil war itself.
The author mentions that: "Southerners adopted beliefs that justified slavery as a moral good, such as the view that slavery benefited slaves because it offered them a better life than they would otherwise have as freed people."
The law was changed, but this belief was still held by the defeated southerner ruling class, who began using weasel tactics as a method of enforcement (example: Jim Crowe). These tactics were initially fought by federal power, but the political will to carry on this fight faded over time. I fret to think of the US that could have been, had this fight been given the attention it deserved.