Utopian and Scientific is mostly the introduction and first chapter of the Anti-Dühring, which is in my opinion Engel's finest philosophical work. I find Engels much easier to understand than Marx, and in the Anti-Dühring he goes through the entirety of the Marxist philosophical framework while giving examples and dunking on Dühring and other liberals and utopian socialists. See for instance the beginning of chapter 10 where Engels talks about the pitfalls of thinking in abstractions, which I find infinitely quotable.

We have already had more than one occasion to make ourselves acquainted with Herr Dühring’s method. It consists in dissecting each group of objects of knowledge to what is claimed to be their simplest elements, applying to these elements similarly simple and what are claimed to be self-evident axioms, and then continuing to operate with the aid of the results so obtained. Even a problem in the sphere of social life

“is to be decided axiomatically, in accordance with particular, simple basic forms, just as if we were dealing with the simple ... basic forms of mathematics” {D. Ph. 224}.

And thus the application of the mathematical method to history, morals and law is to give us also in these fields mathematical certainty of the truth of the results obtained, to characterise them as genuine, immutable truths.

This is only giving a new twist to the old favourite ideological method, also known as the a priori method, which consists in ascertaining the properties of an object, by logical deduction from the concept of the object, instead of from the object itself. First the concept of the object is fabricated from the object; then the spit is turned round, and the object is measured by its reflexion, the concept. The object is then to conform to the concept, not the concept to the object. With Herr Dühring the simplest elements, the ultimate abstractions he can reach, do service for the concept, which does not alter matters; these simplest elements are at best of a purely conceptual nature. The philosophy of reality, therefore, proves here again to be pure ideology, the deduction of reality not from itself but from a concept.

And when such an ideologist constructs morality and law from the concept, or the so-called simplest elements of “society”, instead of from the real social relations of the people round him, what material is then available for this construction? Material clearly of two kinds: first, the meagre residue of real content which may possibly survive in the abstractions from which he starts and, secondly, the content which our ideologist once more introduces from his own consciousness. And what does he find in his consciousness? For the most part, moral and juridical notions which are a more or less accurate expression (positive or negative, corroborative or antagonistic) of the social and political relations amidst which he lives; perhaps also ideas drawn from the literature on the subject; and, as a final possibility, some personal idiosyncrasies. Our ideologist may turn and twist as he likes, but the historical reality which he cast out at the door comes in again at the window, and while he thinks he is framing a doctrine of morals and law for all times and for all worlds, he is in fact only fashioning an image of the conservative or revolutionary tendencies of his day — an image which is distorted because it has been torn from its real basis and, like a reflection in a concave mirror, is standing on its head.

Since you've already started it you might as well continue reading it.