Babel 17 from Samuel Delany. It introduces me to language sciences, human sciences, and then humanism. It switched my point of view on all sciences, and on people too. But for people it also come from one or two other shorter novels from the same author. It was in the same book though. It somehow came during the holidays between high school and university, so like a coming of age thing. I will always remember it.

Another one is not from a book but a video game. Kotor2. At some point, you are asked by a ghost to take position. If you don't, you are answered "apathy is death", and all ghosts, friends and foe, attack you. It was almost traumatic : I learned with this that sometimes you cannot be neutral, you must make a choice that will have consequences, and you will still have to endure the consequences. I will always remember this : apathy is death.