Adults are dull, imagination-less creatures. They are literal, and the only truth is the truth they see with their eyes, trapping them within their self-made limitations.
A worldwide best seller since its publication in 1943, the book remains very much a thing that adults give to children, rather than something many children would choose themselves. It's really a book for adults. The protagonist is not the young prince but rather the middle-aged Aviator who narrates the tale.