My limited knowledge of Italian history doesn't extend much past ww2, however I've been doing a fair amount of basic research online. I've mostly read bits on the years of lead but certainly nothing academic- and I'd like the historical context for that period, particularly postwar fascism.
Édit: missed my actual question, i meant this to be 1945-55 or so? But literally any political history, history of Italian political thought etc.
I strongly recommend 'The government of republican Italy' by Adams and Barile. (I have the second and the third editions. The third is more up to date but it cuts out some material on the period you are interested in, so I'd recommend the 2nd edition if you can find it.) The book focuses on the institutions of the Italian state and how they work in their cultural context, so it provides a good overview of politics, society and economics in Italy during the post-war period. It deals extensively with the ideological positions of the major political parties and specifically looks at fascism, anti-fascism, and the constitution making process.
A good accompaniment to Adams & Barile, if you are interested in post-war Italian political thought, is 'The idea of the republic' by Viroli and Bobbio. It is not primarily a work of history; it is, however, a discussion of Italian politics and Italian political thought through the eyes of two leading Italian thinkers, Noberto Bobbio, a liberal in the tradition of Cavour and Einaudi, and Maurizio Viroli, a civic republican in the tradition of Machiavelli and Mazzini.