Choose your own adventure books. For some reason I wikipedia'd them today and discovered this entry about one called Inside UFO 54-40. This is an excerpt from the wikipedia entry:
"One book, Inside UFO 54-40, revolved around the search for a paradise that no one can actively reach; one of the pages in the book describes the player finding the paradise and living happily ever after, although none of the choices in the book led to that page. The ending could only be found by disregarding the rules and going through the book at random. Upon finding the ending, the reader is congratulated for realizing how to find paradise."
It's sort of existential for a children's book series! It's intriguing. Makes you wonder how many people figured it out and what lesson they took away.