If you are wanting a broad overview of both, primary sources are gonna be better suited to understanding nuance and the changing factors in their context. Reading the Ordinances of Secession, for example, will help you understand the reasoning (as stated at that time) for secession, just as Lincoln's inaugural can help understand his feelings addressing a nation on the brink of Civil War.

BUT, that all really needs to come after understanding the basics from multiple angles, which is really only available in secondary sources. The two best works on either subject are James McPherson's Battlecry of Freedom, and Eric Foner's History of Reconstruction, but you'd be just fine with the condensed A Short History of Reconstruction. Both are seminal works that have withstood the test of time. Read those, then you will be better equipped to go more in depth into the primary sources.