#30 Stranger in a Strange Land by Robert A. Heinlein
What to say. This is a book that I had read years ago, but a reread recently made me add it to this list. Written in 1961 before the flower child era, before hippies and the space race, this was another groundbreaking sci-fi book that is overlooked by the recent generation.
Right before world war III, a large ship is sent to Mars and looses contact with Earth. Twenty-five years later, another craft lands on Mars and makes contact with the native martians. They find out that the earlier spacecraft had one survivor, a small child that is now 25 years old. He returns to earth.
He inherits all the wealth of those that went to mars, and by a quirk of the law, technically owns Mars. So being wealthy beyond belief tries to explore and understand Earth and its people. He has never seen women, had sex, seen our world, understood food, laws, or religion.
Good fantasy lets you get away, good science fiction does as well. However, the great science fiction takes you to another place and makes you think. Looking at life. This consists of a deep dive into what it is to be human, and what we are and could become.
A religion has formed that is superconservative, except in their churches. As a good and faithful person you can get a pass to participate in any debauchery, gluttony, or vice that interests you, while you are there. A look into a religion that requires you to be conservative, but lets you cast that away if you wish for a time.
All of this was fascinating to me, and though I do not agree with many of his conclusions about the human race, I did find it interesting. He is considered one of the big three sci-fi writers of the 20th century, along with Asmov and Clarke, and it is well deserved. He tries to get to the core of what is human, what we are and what we can be.