I was sort of bummed to see several people mention A Stranger in a Strange Land, but that was the first book to come to mind. I have memories that I think came from that book to this day. “Grok,” of course, but “What color is that house on the hill?” “White…. on this side.”
That was one of my most important lessons in not extrapolating from too few cases.
There was the Asimov Foundation series too, that I read over and over, dreaming of a time when we would be knowledgeable enough to control our future fairly precisely. You can see that series’ influence in so much of my life. I think I met the good doctor only once, though.
Like others, A Wrinkle in Time is on my list. It is one of the few books I read more than once, in my life. I must have read that book a dozen times or more. I think, subconsciously, I must have totally identified with the family in that story.
Then, I’ll throw in a couple of others from childhood, just to see if anyone knows them. Folly My Leader, about a boy who is blinded by a firecracker and has to go to school to learn how to use a guide dog.
There was another one about being a stewardess, that I read over and over, but I don’t remember its name. There may have been a character named Patricia in it.
Finally, I have to mention the Wizard of Oz. I read the whole series several times, and was absolutely thrilled at the magical world they inhabited. It’s a world I wish I could live in, too.