Peter, the single-best review of counter-cultures and their location in social history (that I know of) is here: https://meaningness.com/countercultures . That page is the intro to a sequence of chapters, and is part of a bigger book. I have found it quite fun to read.

As to postmodernism, there just seems to be a whole lot of misunderstanding of what it is. “I can’t come to bed yet; there is someone wrong on the internet”.