Much has been written on the subject, but I've yet to find any source that I would consider credible. The two best examples that I've found are this article and this article.
The first article claims that "Yet apparently many today are still deceived, are deliberately deceived, and even prefer to be deceived" about the true causes of the war. Sadly, this historical revisionism has reached back in time and brainwashed the legislatures of all of the seceding states as well as the highest representatives of the new government that they established. You want proof? Go read this entry. Or better yet, go google the original declarations of secession. It's not 'revisionism' when it predates the war itself, especially when directly propagated by the people who started it. The article also calls the process of secession 'constitutional.' The fact that it is nowhere mentioned in the constitution leads one to believe that the author is 'making things up'. He also references a fake definition of 'civil war' in which a war for independence cannot be so considered (Wiki says: "A civil war is a war between organized groups within a single nation state, or, less commonly, between two countries created from a formerly-united nation-state. The aim of one side may be to take control of the country or a region, to achieve independence for a region, or to change government policies"--how does this not cover the American Civil War?), elides the difference between imports (taxed) and exports (not taxed), provides no citations for any statistics or figures, and quotes Karl Marx in support of his argument.
This raises three larger points: first, if there was a difference in economic policies favored by the North and the South, then the difference was inextricably bound up with slavery. Why were tariffs an issue? Because of slavery, not only because of the agrarian economy that it propped up, but also because, as Calhoun feared, industrial viability would lead to decreased slave population and Abolitionist success. Second, in a debate over economic policy, if each region supports the policy most favorable to it, why is it the North's fault that the South seceded? If indeed each was merely arguing for its own self-interest, then neither and both are to blame. Third, even supposing that slavery was merely the rallying cry that the South used because it couldn't get people worked up enough over taxes, it raises the question: what kind of horrible people use maintaining slavery as their casus belli?
The second article is a rather boring screed, but as I said it was the best I could find. Rather than answer its individual points, I will simply address its closing paragraph:
I shall conclude this article with a passage written by John Reagan, Postmaster General of the Confederacy. "You are not content with the vast millions of tribute we pay you annually under the operation of our revenue laws, our navigation laws, your fishing bounties, and by making your people our manufacturers, our merchants, our shippers. You are not satisfied with the vast tribute we pay you to build up your great cities, your railroads, and your canals. You are not satisfied with the millions of tribute we have been paying you on account of the balance of exchange, which you hold against us. You are not satisfied that we of the South are almost reduced to the condition of overseers of northern capitalists. You are not satisfied with all this; but you must wage a relentless crusade against our rights."Very fine-sounding indeed. Unfortunately, the quote is truncated, whether through stupidity or dishonesty I cannot say. The fact that it was truncated mid-sentence, however, argues for dishonesty--he actually said "our rights and institutions"--meaning, of course, our peculiar institution, as he explains in the very next sentence:
And now you tender us the inhuman alternative of unconditional submission to Republican rule on abolition principles, and ultimately to free negro equality and a government of mongrels or a war of races on the one hand, and on the other secession and a bloody and desolating civil war ... Our own Government succeeded because none but the white race, who were capable of self-government, were enfranchised with the rights of freemen. The irrepressible conflict propounded by abolitionism has produced now its legitimate fruits-- disunion. Free negro equality, which is its ultimate object, would make us re-enact the scenes of revolution and anarchy we have so long witnessed and deplored in the American governments to the south of us.'Nuff said.