I just finished reading William Freehling's second volume of the Road to Disunion this evening. It is a tremendous and riveting book, a rewarding read. I always recommend Freehling when people ask me about Southern history or Civil War era books, so you had better add this one to the stack if those things interest you.
It has Freehling's notable finely calibrated interpretations of every issue, and each section is rich in new arguments and new stories, and recasting of other stories you might think you know. He very firmly and conclusively identifies slavery as the cause of the war (yes, this is still disputed by southerners and fellow travelers) and does so masterfully by so completely describing the conflict between democracy and despotism that slavery produced and by tracing the potency of ideas of white egalitarianism within the South. He has a real eye for contingency, which I think is perhaps the most important thing.
I do think the first volume is a superior book, but this one is essential reading.