All I can do is add ...

David M. Potter's book The Impending Crisis: 1848 - 1861 is THE go-to source to understand how and why the Civil War broke out in 1861.  It's also the go-to source for understanding why it didn't start in 1850 when it came this -><- close to so doing.  And why Stephen Douglas pushed through the Kansas-Nebraska Act, obliterating all previous compromises:  he wanted to build a railroad.  (And on and on and on.)

By reading Goodwin you've already got an overview of Potter.  Reading the book will fill out your understanding of why & how of our Civil War.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre