Consider other books by Antoine de Saint-Exupéry, especially Wind, Sand and Stars, a memoir about the author's aviation experience.
There are many children's books with a philosophical edge as well, such as The Wizard of Oz or Winnie the Pooh. Alternatively Little Women or The Perks of Being a Wallflower are similar coming-of-age books. Peter Pan provides a different angle on eternal childhood / childishness, which is developed further into the adult perspective in the film sequel Hook.