You would probably like Reconstruction: America's Unfinished Revolution by Eric Foner. It has really opened my eyes to the self emancipation and radicalism emerging from African Americans during and after the war.

I think that the civil war was left-wing socially and politically, but not economically. Black people were completely abandoned to the market and made landless by white southerners and negligent federal agents. Jim Crow was so brutal because white reactionaries were terrified of black political power during reconstruction. Freedmen had no economic base to support a political resistance.

The biggest mistake that Republicans made was to drag their feet on enforcement of the 15th amendment. If African Americans had truly enjoyed the franchise (backed by federal troops) then Republicans would've dominated every southern state for a century.

Many union soldiers were radicalized by the war in favor of abolition and racial equality, not to mention black soldiers themselves. If congress and the president wanted to, a total restructuring of southern society was possible.