I take it you mean Eternal Fascism: Fourteen Ways of Looking at a Blackshirt.
It’s interesting as an outline of the ideology of fascists, but I think I’ll hang on to a preference for a functional definition, since it describes my immediate concern: bands of thugs beating up my friends, family, and comrades. In the last paragraph, Eco says,
It would be so much easier for us if there appeared on the world scene somebody saying, “I want to reopen Auschwitz, I want the Blackshirts to parade again in the Italian squares.” Life is not that simple.
Which rather misses something critically important, which is that you do find people saying similar things, and worse, acting on them and attempting to organize around them: there are overt fascists in the world, and they actually use violence against those trying to resist oppression. It’s valuable to think about the cultural and ideological aspects of a social and political movement, but I think it’s a mistake to assume they’re more important than the concrete, practical aspects, and of course it’s worse to outright deny the existence of concrete, practical aspects.
My sense of Eco is that he’s a classic example of what Marxists call an idealist (it has a different meaning than in most other contexts, which often confuses people), in that he tends to emphasize ideas rather than material relationships as the driving force of history.