I'm affraid I must disagree. If you read history books shortly after the Civil War - up to the late 1930s - you'll find that slavery was hardly mentioned as a cause of the war. Neither North or South fought, specifically - or primarily - to end slavery. State's rights, and the North's invasion of the Southern states were the main cause - though you could argue that was precipitated by concerns over Lincoln's stand on the South's refusal to end slavery. Even that, though, is a red herring as the South offered to end the slave trade - and by etension, slavery - but were met with resistance (and some say a threat to secceed) from the New England shipyards and the states where they lay.
In fact, a number of attempts - by a number of means - were proferred to end slavery, but the North wanted it ended overnight. This, of course, sounds simple enough - but not when the South's entire economy was at risk. So, while the South was willing to phase out slavery over time - the North was not. And while this was a contentious issue, the South felt it could be resolved peacefully. In the South the tipping point was Lincoln's provocative open recruitment of 75,000 volunteers to invade the southern states - who did indeed see themselves as a collection of individual "countries" of a sort. Case in point: Robert E. Lee would easily have taken the offer of command of Union forces had not Virginia seceeded. But with the secession of Virginia Lee could not bear to "raise his sword against his countrymen."
It's a tedious issue indeed. But the biggest mistake when observing - and criticizing it - is doing so with today's morals and attitudes. A true historian (a double M.A. myself) knows that the biggest mistake we often make is judging people and events of the past through the lens of today when things were quite different in the past. Even terminology can change drastically from generation to generation, much less over numerous generations.
To conclude, I see the Civil War as a fight over state's rights and continued and evolving central governmental control - with a number of issues at the forefront. Economic issues, moral issues, religious issues, state's rights - and, yes, slavery - all contributed to the coming of the war. You could almost equate that era with today's, as the government continues to insist on more and more control - womb to the tomb, as they say - and a growing number of the populace rebelling against an ever-bigger number of the populace who seem content to live off governmental handouts. Those governmental handouts, of course, come from the toil of the first group who's growing tired of paying for the pleasures enjoyed by the second at their expense. At their expense, of course, because the government has only the money they take from you and I. It's not unreasonable to assume that, at some point, a "Civil War" will develop over these and many other currently contenteous issues - and some historian in the future will blame it all (falsely) on the "rich getting richer", "Not paying their fair share", etc - when we all know there exists a cornucopia of reasons, when boiled together to raise the temperature in society as a whole, something/some faction will have to give (as they say).
As for the issue of blacks fighting for the south - it's one of the least known facts of the Civil War. Stonewall Jackson's brigade had hundreds of blacks serving as both fighting men, and teamsters, cooks, etc - just as whites did. And the 8,000 figure proferred may be woefully low. The true number may be as high as 20-25,000. And they fought not because they were promised their freedom (though some were), but for the same reason everyone in the South fought. Because their homes, their way of life, and the fruit of their labors were being invaded and destroyed - and the Union soldiers they came across generally cared about as much, or less, for them as did the Confederate soldiers who fought alongside them.