A book by one of the more difficult to understand thinkers of the 20th century about by far the most difficult to understand philosopher of the 19th century is obviously not a browse over breakfast affair. The good news is that for readers of either man, this is actually quite engaging. But really, it's only for those already acquainted with the whole range of jargon they use. If you don't have the time or inclination to absorb it, your time would be better spent with Marcuse or McDowell. No shame in that.
Because of all this, I suspect that the readership of Hegel: Three Studies is quite small, which is a shame. Any reader will come away disabused of two common beliefs: first, that Hegel is merely a reactionary totalitarian stooge; second, that Adorno is a fierce critic of German Idealism. The former has been put paid to by recent Hegel scholarship, but often at the price of re-enforcing the latter. So, despite the efforts of Brandom, McDowell, Pippin etc... to salvage Hegel's reputation, I can still heartily recommend this book, both as a corrective to bad readings of Hegel, and, still more, as a corrective to bad readings of Adorno.
The book itself comprises three essays. The first is by far the best. 'Aspects of Hegel's Philosophy' lays out the key element of Hegel's thought: the complete mediation of objectivity by the subject, which leads not to relativism, but to a more robust theory of truth than correspondence theories can provide. This is because only complete mediation can make the object normative for the subject; that is, only by mediating it fully can the subject cease to be alienated from the object. This would seem to give rise to the Subject as All Devouring Maw. But Adorno argues that Hegel's own theory makes it impossible to reduce the object to the subject, despite what he may have wished: an absolute subject would deny the very possibility of objective normativity. This contradiction within Hegel's philosophy points us toward the context for the thinking, and this will be perhaps the most difficult part of the book for pure philosophers. Adorno's quasi-Marxism is very difficult to get a handle on (I recommend Lukacs' "History and Class Consciousness" essay as a companion piece here, although it is substantially less sympathetic towards Hegel), but is essential for understanding his reading of Hegel. In short, modern capitalism makes possible freedom from nature's domination, but in turns 'naturalizes' what was previously cultural: that is, we come to see our social institutions as natural and unalterable. In this situation, 'facts' which could be overcome (e.g., world hunger) are taken as logically necessary, as given. Hegel is correct to see the existence of a subjective absolute, but wrong to argue that it is *our* subjective absolute. Rather, it is a 'second nature' which must itself be overcome. Adorno argues that the truth of Hegel's system is that it is inconsistent - the State becomes the ultimate guarantor of the absolute, but the State is treated as a given, as alienated from us. Hegel's discomfort with this position points us out of the system as he has described it.
All this yields the conclusion that for Hegel, truth is not ontological, but it is objective; that truth is historical, but not relativist; that the concept is mimetic, but also more than mimetic; and that Hegel is a kind of rationalist utopian who criticizes the Subject on the basis of what it could be: the condition for the freedom of subjects.
The second essay, 'The Experiential Content of Hegel's Philosophy,' is more uneven. It repeats many of the themes from 'Aspects,' while giving a more robust account of Hegel's critique of positivism, and the problems of this critique. The concept of 'totality' gets a pretty bad press these days, but Adorno makes a convincing case that we can't do without it: no meaningful critique of our world can proceed without acknowledging that our world just is a totality. At the same time, to merely affirm the totality is insufficient, as our experience of the world tells us. We experience contradiction when we sense that the whole is systematic but irrational.
The final essay, 'Skoteinos,' is a guide to reading Hegel, which isn't particularly helpful on that score. It does, however, provide some insight into Adorno's conception of philosophy itself, and argues against the prevalent practices that go under that name (positivist neuro-philosophy; Wittgensteinians etc...). Adorno's final position on reading Hegel is that a true reading will remain dialectical - insist on a tension between concept and object - whereas Hegel understood himself as abandoning the dialectic by identifying concept and object.
In short, if you're among the many people who have rejected the Hegelian tradition in favor of some version of post-structuralism, you might like to check this out. I'd like to think it's enough to change your mind.