This short little book on the primary Fascist theorist and ideologue, Giovanni Gentile ( -- who comes, like Croce and Stefanini, out of the Subjectivist school of Italian idealism), is a tour du force, and I recommend it highly to anyone interested in the subject of Fascist thought.
This book contains a fascinating (and largely correct) analysis of the metaphysical foundations of Marxism -- especially of Marx -- which Gregor rightly understood to be connected not with the mechanistic traditions of the British materialists, to whom Marx (as early as the Notebooks) explicitly opposed; and which was, indeed, the materialism of Engels, and then of Lenin), but rather to the pragmatist/vitalist traditions associated with Priestly's notion of 'living matter' -- which Marx thought was derived from the materialism of Epicurus (a topic to which Marx devoted his dissertation). This is the metaphysical underpinning, by the way, that justifies the 'humanist' interpretation of Marxism, from Mondolfo onwards.
It's a fabulous book -- and though Gregor himself is a fascist (he was strongly influenced by Julius Evola), and sometimes maintains slightly eccentric positions - he is still the most perspicacious student of the topic writing in any language, in my opinion.