Good reading in preparation would be “Southern Wealth and Northern Profits” by economist Thomas Kettell, a book written just before the war began with an emphasis on the financial relationship of the two sections.
Then, as the prelude to the beginning of the war, I would heartily suggest “Allegiance” by David Detzer.
If you only have time for one, I would strongly recommend “Days of Defiance” by Maury Klein, who I think is one of the best American historians.
Do not forget the Anti-Federalist papers. We would have been in a better position had more heed been paid to the anti-federalist arguments.
Thirdly, the absolute command of Congress over the militia may be destructive of public liberty; for under the guidance of an arbitrary government, they may be made the unwilling instruments of tyranny. The militia of Pennsylvania may be marched to New England or Virginia to quell an insurrection occasioned by the most galling oppression, and aided by the standing army, they will no doubt be successful in subduing their liberty and independency. But in so doing, although the magnanimity of their minds will be extinguished, yet the meaner passions of resentment and revenge will be increased, and these in turn will be the ready and obedient instruments of despotism to enslave the others; and that with an irritated vengeance. Thus may the militia be made the instruments of crushing the last efforts of expiring liberty, of riveting the chains of despotism on their fellow-citizens, and on one another. This power can be exercised not only without violating the Constitution, but in strict conformity with it; it is calculated for this express purpose, and will doubtless be executed accordingly.
Prophetic.