I did not see any main point that Tyson was trying to communicate in this book. While there are chapter divisions, the reader sees him pontificating on various social issues with no connection between the material. In the Preface, Tyson states that societal ills could all be solved by people thinking as scientists. If we could just see earth as the Apollo astronauts did, our differences would disappear. Scientists are the only objective people on the planet. Scientists do not have opinions, they just have facts.
As I was reading I kept looking for the reason that the book was written. I didn't find one. I did notice, however, that there were two ideas repeated in every chapter. First, he is concerned how visiting space aliens view humankind. I don't know why he is upset about this as there is no scientific proof that aliens exist. Remember, all scientists are objective and only deal with facts. Second, Christianity is the reason for all of the problems in the world. Tyson states that the God of the Bible demands competition among his earthlings which promotes racism, colonialism etc..., as well as the idea that Christians are superior to non-Christians. He cites at least one verse from Genesis in each chapter to prove his points. I have to say that he has a psychological complex about the Bible because he has written about it so much in this work. So what if he's an atheist. But when someone can't stop writing and talking about the Bible in this way, he has a personal problem separate from being an atheist.
The material was not over my head. This is not a scientific book. It is about society as a whole from caveman days to the present. With the two main ideas presented in each chapter being ideas that have not been proved by science, why are his "objective" "opinions" being touted as truth? Also, I got the impression that he feels superior to us regular folks who are not scientists. Superiority runs deep in this work. Again, I had to wonder how he became superior to everyone else since God is the entity requiring superiority from his followers and Tyson is not a God follower.
The book was a disappointment. I expected a scientific book. What I got was unorganized ramblings regarding problems on earth. The writing itself was good but the content was lacking. I am rating it 3 out of 5 stars.