I thought I had understood dialectics through reading Mao's philosophical essays many years ago but now realise that I hadn't understood the initial non obvious phase of concept formation, particularly the importance of history and abstraction in that process. eg. how in Capital Marx identifies the concept of value.
I suspect the disagreements from non marxists and misunderstandings from "marxists" that have followed are partly to do with not understanding the method used. There is a section on method in A Contribution to the Critique of Political Economy but it is not particularly thorough. Marx applied a method to analyse the internal workings of capitalism but only left hints as to what his method was, rather than a full explanation, for whatever reason. This footnote from EP Thompson towards the end of chapter one of Saad-Filho provides the explanation:
‘We have often been told that Marx had a "method" ...and that this constitutes the essence of Marxism. It is therefore strange that ...Marx never wrote this essence down. Marx left many notebooks. Marx was nothing if not a self-conscious and responsible intellectual worker. If he had found the clue to the universe,he would have set a day or two aside to put it down. We may conclude from this that it was not written because it could not be written, any more than Shakespeare or Stendhal could have reduced their art to a clue. For it was not a method but a practice, and a practice learned through practising. So that, in this sense, dialectics can never be set down, nor learned by rote.’