I fortuitously found this book in a chaotic bookstore after it was brought up on one of Matt Christman's "Grill Streams" (Which I can't recommend enough, the perfect synthisis of Zizek and Mark Fisher). It was referenced as THE book on post WW1 German politics, and that is an understatement.
If I had to draw one thesis from Eberhard Kolb's "The Weimar Republic", it's that it cannot be understated how much the German Social Democratic Party blew it. This was the party who's strict historical mission was to fulfill the Marx's transition from imperial capitalism to socialism in Germany, and they blinked until they opened their eyes in the Third Reich.
The majority of German soldiers and workers who revolted to end WW1 were SPD supporters, and instead of harnessing that mass popular power they capitulated to the anti-democratic upper and middle classes at every turn. When the former/current monarchists wanted a president who had the power of the old Emperor, the SPD gave it to them against warnings that if one of the old Generals took that position they'd crush the parliament (that's exactly what happened). When the (often overestimated) communists rose up to do what the SPD was too afraid to, they organized paramilitary Freikorps (that turned into Brownshirts a few years) later to slaughter them. To draw allusion to the present, "a principal weakness... lay in the contrast between 'far reaching social intervention by the state and the almost unlimited autonomy of big business in matters of price fixing and market policy". To summarize, "...just as they had not followed the revolutionary-socialist course to the end, so they failed to tread the liberal-democratic path consistently...". They boofed it, gave Hitler an open lane, and have become the historical reason so many on the left don't trust social democrats.
This books is both extremely academic and a surprisingly easy read. The first chunk of it is a straightforward history of the period from 1918 to 1932, separated into both chapters and subjects. The latter half is full of conclusions anyone will find interesting mixed in with historiography that anyone who isn't a German historian from the 1980's will find pretty boring. But despite that, this book fundamentally challenged the socially focused narrative of "why the Nazi's came to power" I had grown up with, and made a well cited and compelling argument from examing the political economy of the intervening period. If this subject is at all interesting to you, you owe it to yourself to give this book your time.