As a general introduction to Fascism - as a XX Century European phenomenon, and therefore mainly focusing on Italy and Germany - I'd recommend starting from R. Paxton's The Anatomy of Fascism [2004]. Alternatively - but it's a lukewarm recommendation - S.G. Payne's A History of Fascism, 1914-45 [1995] should cover similar grounds.
More specifically for Italian Fascism, an attempt at a comprehensive coverage of the social and political landscape during the "formation years" of Fascism, can be found in R. Vivarelli's Storia delle origini del Fascismo [three vol. 1965-2012], which, as far as I am aware, has not been translated. Also of interest his collection: Il fallimento del liberalismo [1981]; which deals in part with the arguments exposed by C. Seton-Watson in his Italy, from liberalism to Fascism, 1870-1925 [1967]. All of these works are somewhat dated in their historiographical foundations, if not in their interpretation of Fascism (I do, in good measure, agree with Vivarelli's reading). The greater scope in Vivarelli's approach is nonetheless quite unique in a field populated with monographs mostly dedicated certain specific aspects of Fascism.
Of interest - and also non traslated - in order to examine the same context of Vivarelli's work from a more particular angle, S. Colarizi's Dopoguerra e fascismo in Puglia (1919-26), 1971; and A. Roveri's Le origini del Fascismo a Ferrara, 1918-21, 1974.
For an approach to the development and definition of Fascism in Italy from a "cultural" angle, the obvious recommendation are the many works on the matter published by Emilio Gentile (whose works have the additional quality of being, some times, available in an English translation). He has spent a good portion of his career analyzing the early stages of the ambiguous definition of a "fascist ideology" within the environment of what he has defined "national radicalism".
His early works that focus especially on this process - Le origini dell'ideologia fascista (1918-25) [1975, 1996] and Il mito dello stato nuovo dall'antigiolittismo al fascismo [1982, 1999] - provide a good insight into the context of the transition from the ideas of the Italian liberal state to those advocating for a new, albeit often ill defined, political system. Since both are somewhat technical in their perspective, I would suggest pairing them with a general overview of Italian politics during Giolitti's age and the Great War unless one is already familiar with the period.
For this purpose, I'd recommend both the works of R.J. Bosworth - Italy, the least of the great powers [1979], Italy and the wider world [1996], Mussolini [2002] and Mussolini's Italy: Life Under the Dictatorship [2005] - and those of H.J. Burgwyn - The legend of the Mutilated Victory: Italy, the Great War and the Paris Peace Conference, 1915-19 [1993] and Italian foreign policy in the interwar period, 1918-40 [1997]. Both authors are generally accessible even if you aren't a specialized reader, even if each work does focus on certain more specific aspects. Also, somewhat more specialized, from a perspective on the economical side: Forsyth, D. - The Crisis of Liberal Italy [1993]
Still with Gentile, and for additional context, his early work on La Voce - Mussolini e La Voce [1976], especially for the influence of Prezzolini's newspaper on Mussolini's (tenuous) attempts at developing his own revisionist approach to Marxism - Il culto del littorio. La sacralizzazione della politica nell'Italia fascista. [1993], a significant contribution to the Fascist attempts at reshaping national culture by way of myths and symbols summarized in a sort of "political liturgy" - La Grande Italia [1997] for the affirmation of a new sentiment of Italianismo during the early XX Century - "La nostra sfida alle stelle", Futuristi in politica [2009] for the origins and relative impact of Italian Futurism as a political formation - Mussolini contro Lenin [2017] for a review of Mussolini's "anti-Bolshevism" during 1917-22, mostly taken from the pages of his Popolo d'Italia and for an attempt at a critical examination of how Mussolini's "revolutionarism", or instinct for a national renovation, could adjust to the impact of the Bolshevik revolution.
For a more detailed coverage of Mussolini's political trajectory, one should also refer to De Felice's extensive monograph Mussolini, [eight vol. 1965-97]. As well as De Felice's additional works on the relations between Mussolini, De Ambris and D'Annunzio centered around the "Fiume endeavor" (for context on the latter, one should check the detailed but otherwise somewhat dated work by P. Alatri Nitti,D'Annunzio e la questione Adriatica [1959])
In more recent years, prompted by one of the many "revisions" within the historiography of Fascism, specific works have attempted to cover Mussolini's experience as a more or less prominent figure of Italian socialism and his eventual transition to revolutionary interventionism and then to "national" interventionism. For a basic, but somewhat technical, summary: Di Scala, E. ; Gentile, E. - Mussolini 1883-1915, Triumph and transformation of a revolutionary socialist [2016]
A more "technical" - and in itself not exempt from controversies - work in Z. Sternhell's well known The Birth of Fascist Ideology [1989]. Which, unless you are familiar with the subject, I would only recommend in so far as establishing certain ideological traits of national-syndicalims which influenced the early fascist movement and continued to represent a portion of the internal dialectics of Fascism (precisely, even if a discussion of this point would probably exceed the limits of your interest, I do not agree with his conclusion that, in its core, Fascism can be identified, even from an ideological perspective, with national-syndicalism).
As you can see, most of this works agree with my main interest which is the early stages, ideological formation and political affirmation of Fascism; rather than with the proper "Regime" stage. If that's the part you are more focused on, I'd probably be able to come up with further suggestions.
For instance, now that I think about it, P. Corner's The Fascist Party and Popular Opinion in Mussolini's Italy [2012] should be of some interest, and also relatively accessible.