Possibly the most beautiful book of the twentieth century, the Little Prince will appeal to the hearts of adults and children alike. It tells the story of a little prince, who falls to earth from a star, and of the airman, stranded in the desert by the crash of his place, who seeks to understand the prince's secret. The premise is simple and the story simply told, and yet Saint-Exupery creates a tale that is full of poignancy and hope.
As the little prince journeys the planets around his own home, Asteroid B612, he encounters a variety of individuals: the Conceited Man, the King, the Accountant, the Drunkard, the Geographer and the Lamplighter. Each one becomes a parable of human nature: or rather, the nature of adults. The Little Prince is a story about childhood, mortality (made all the more poignant by the fact that Saint-Exupery died in action in WW2, the year after the book's publication), friendship, love, hope and the magic in our lives that we are at risk of losing as we grow older. For me it held enormous personal emotional value.
If you can manage to read it in the original French then by all means do, but any translation still conveys some of the treasure in Saint-Exupery's words. Personally I recommend the Wordsworth Children's Classics edition for its translation, if not the poorly reproduced illustrations, but I think I may just have a personal bias for the first edition I read.
For a so-called 'children's book,' this is one that will live with you for the rest of your life.