This is by far one of the best expositions of Dialectical thought available. Ilyenkov explains dialectics dialectically, that is, he does not define dialectics but narrates its development in different moments, showing how its contradictions change over time throughout the philosophies of different thinkers, and how it eventually develops into Marx's particular conception. The section on Spinoza in the first half is of particular note, considering the bad rap Spinoza gets from some Marxist circles (generally the more established, militant circles) against others (usually academic) as his thought has become associated with Deleuze, and therefore also with the many often bizarre directions his thought has led others.
The book is structured in a similar fashion to that of the Critique of Pure Reason, with the first part serving as an analysis of the thinking tools, and the second as a methodological use of those tools to serve as examples. Many of the essays, however, do not flow logically into each other, which makes the reading of the book tortuous at times, especially in the second half.
Without a doubt, while the second half has essays that are of extraordinary importance, the weakness of others makes the work as a whole rather strange. This is to say that the method is not always consistently applied and that it is unfortunately very evident when Ilyenkov's argument is clouded, avoiding potential landmines in his wording which could have put him at odds with the authorities around him, many of which worked with a positivist Marxist approach, or a vulgar materialist one. In this sense, however, his exposition of Hegel's importance and his admiration (and his important points about Lenin's love for Hegel, especially) for Hegelian thought in Marx, is extraordinarily well put, and incredibly useful for anyone first seeking to approach the problems of Dialectics.