One of the best insights we can gain from this book is that virtually everything we think and do is driven by ideas. And these ideas are not fixed and eternal. They have a history and that history shows that people in other places and times thought quite differently about those ideas and because of that lived differently as well.
If you change your ideas you can change your life. But, it's not immediately obvious that we really can change our ideas about family, time, work, love, money, travel, or death. It's not obvious until we see examples of people who lived in the past with different ideas about these things.
The point of looking to the past is not simply to go back to living in the past or to learn the lessons of history so that we don't repeat them. Rather, it is to see that we can view our own lives as open to being re-designed. We can experiment with different ways of thinking and different ways of living because the rules governing the important areas in our lives are not as fixed as we usually think.
Yes, money is an important part of our lives but that doesn't mean that we can't determine how important and why. Yes, death is inevitable but that doesn't mean how we relate to it or deal with it is because how we think about these ideas is not inevitable. Knowing this makes our store of ideas richer. And, that's part of the point. As Krznaric quotes Goethe: "He who cannot draw on three thousand years is living hand to mouth."
By looking at the history of these ideas we can see that some of them were much larger in the past and we have allowed them to atrophy. Others we have magnified and elevated to an extent never before imagined. What might we do with these insights? Who is to say? But, seeing history as a way to gain such insights is a valuable insight in and of itself and Krznaric has given us that in his fine book.