Money and currency is actually a much later development as a method to quantify the debt, in this process, subjective human emotion is removed and replaced with an autonomous and objective economic machine.
From this point, the author gave an alternative interpretation and analysis of human history. His conclusion is that the boom and bust of debt is an important driving force in human history, in this process, the debt bubble becomes bigger and bigger - until the unavoidable explosion of debt crisis. Then there will be a radical breakdown of social order, Finally, a new society is rebuilt, and all the debt from the previous society is canceled - this is a periodic cycle that occurs at a scale of 100-300 years. And the author argued, since the 1970, we have returned to (the beginning) of a new cycle.
You don't have to agree everything that the author claims, but the author is good at telling a story, and it's a fascinating read. My summary is not exactly what the author said, the Wikipedia article the P2P Foundation Wiki [1] has a better summary, it includes transcripts of interviews.
[0] https://en.wikipedia.org/wiki/Debt:_The_First_5000_Years
[1] https://wiki.p2pfoundation.net/First_Five_Thousand_Years_of_...