Like a lot of good books this one gets boiled down in the last pages:

We began this book with a quote which refers to the Greek notion of kairos as one of those occasional moments in a society's history when its frames of reference undergo a shift, a metamorphosis of the fundamental principles and symbols when the lines between myth and history, science and magic become blurred and, therefore, real change is possible.

...our scientific means of understanding the past ...has been advancing with dizzying speed. Scientists in 2020 are ...encountering radically different forms of society under their own feet, some forgotten and newly rediscovered, others more familiar but now understood in entirely different ways.

In developing the scientific means to know our own past, we have exposed the mythical substructure of our social science. What once appeared unassailable axioms, the stable points around which our self-knowledge is organized, is scattering like mice. What is the purpose of all this new knowledge if not to reshape our conceptions of who we are and what we might yet become? If not, in other words, to rediscover the meaning of our third basic freedom. The freedom to create new and different forms of social reality.

That third basic freedom is really what Graeber wants us to follow - starting now, posthaste. And this book is a blueprint of questions and stories that show the way to continue to reconceive who we are and experiment with different social realties. Another way to look at this book is that it is a response to the typical status quo argument that basically says we should just keep hurtling forward with our current wildly unequal social reality because that hippy childlike indigenous shit is unrealistic and humans are greedy bastards, and history proves it. This book responds with a tilt of the head, "Are you sure about that?"