The book is supplementary to the comment, I explained the big picture in my comment. Blackshirts and Reds isn't a call to action or an explanation of what to do, but an examination of fascism and Communism, who they served historically, and the material basis for them.
Voting for Harris won't stop fascism, because it won't stop Capitalist decay. You can even see her trying to appeal to small business owners, attempting to "turn the clock back," in her own campaign. Neither will voting for Claudia De La Crúz, PSL's candidate, nor will Stein, and obviously nor will Trump.
Electoralism cannot solve the conditions giving rise to fascism.
The answer is to join revolutionary orgs like the Party for Socialism and Liberation (PSL) or Freedom Road Socialist Organization (FRSO). Only through organization outside the electoral system does the Proletariat have any hope of steering the ship and seizing the reigns.
The Right puts forward a Ronald Reagan or Donald Trump. They give great speeches and stir up people's emotions. The Left tells people to read a book.
The US Empire is far-right, they can field candidates supporting the status quo in both the DNC and GOP. Liberalism is the status quo, taught from birth. Leftism requires reading, because they don't teach it in school, they censor leftism and shun it. It's a struggle, yes, but it's a winnable one.
Conservativism isn't the same as fascism. Reactionary movements have existed in every form of Class Society, when Capitalism overtook Feudalism it was the holdover Monarchist movements. It isn't a "convenient rallying cry," but an analysis of reactionary vs progressive social movements driven by class interests.
I have no idea what this means. Why do you think MAGA is Socialist?
Written in the 90s, you should revisit it.