The friendly, English-speaking extraterrestrial you run into outside your house is asking you to recommend the one book, movie, or song that explains what humans are all about. What do you pick?
My mind first went to historical topics (I’m an historian), but with many books, the alien would get only a view of one era of history, one’s country’s history, or a specific viewpoint. Perhaps a good world history textbook would give a more comprehensive overview of how man has lived over the ages, and might be able show trends and themes that would show how humans have changed and stayed the same over time. It is true that history repeats itself, and somehow men allow that to happen, or fail to understand the correlations between a set of actions and their probable outcome. For instance, despite whether you call a dictator an autocrat, a despot, or a tyrant, the results are much the same: some groups in a civilization are preyed upon, while others have immense, undefined power. We have learned that while communism sounds idealistically fair, it can never be; it is still a form of totalitarianism. Wealth and power are never equalized. We have some instances of democracy, including our own, and only time will tell if a written constitution designed to preserve the rights of individuals, as well as groups (religions, political parties, men/women), will last where it exists and extend to other countries as a preferred form of government.
An alien would also learn a bit about the geography of the world by where and how civilizations first developed, how the grew, and why some areas of the world are so geographically challenged that their development has been stunted. They’d also get an appreciation of why certain areas of the world have suffered more from boundary disputes and wars.
A history textbook would also include major developments in science, math, and technology and how they affected the progress of various civilizations. Religion, too, at least as far as it affected the course of history, would be included.
Would a textbook, I wonder, give any insight into the hearts and souls of people? By inference it might. On the other hand, a simple book like Chicken Soup for the Soul would give an alien an insight into the way people think and act in different situations, and what motivates them. It depends on what you want to know about humankind: how they have acted over time, and the results of their actions, or the essence of what human being are.