Like Harry Potter, he's a kid with tousled hair.

But unlike Harry, this one never grows up. Instead, he dies a mysterious, haunting death in the Sahara, just as his creator would die a similarly mysterious death a few years later when his aircraft went missing over the Mediterranean. Yet in death, the little boy finds a life his creator could never have imagined, and an immortality and status that in some parts of the world even rivals that of the kid with the scar on his forehead.

Antoine de Saint-Exupéry's The Little Prince, which celebrates its 70th anniversary next month, is a magical story that has racked up its own set of impressive statistics since it was first published in 1943. It has sold 150 million copies worldwide and is available in 267 languages, making it the most translated non-religious book in the world. Its fans include such contrasting figures as Umberto Eco and Madonna. Orson Welles loved it too, and James Dean was so spellbound by it that one of the novella's most famous lines – "What is essential is invisible to the eye" – is engraved on a shrine to the actor erected in 1977 in Cholane, California, close to the site of the car crash that took his life in 1955.

That line is a perfect example of why this book appeals as much to adults as to children, perhaps even more to adults than children. The Little Prince is a hard- to-classify story that occupies that curious world of allegory and fable, rather like CS Lewis's Narnia series or Paulo Coelho's The Alchemist, whose desert setting brings Saint-Exupéry's strange story to mind.

It is certainly an eccentric tale, one that can leave you puzzled at a first reading. The unnamed narrator is remembering the time his aircraft crashed in the desert. While he works on repairs, the little boy of the title appears. He asks the pilot to make some drawings for him and they begin a series of enigmatic conversations that form the heart of the book. These exchanges are full of the illogicality that can so frustrate adults, but which children just happily accept. This is, many believe, one of the book's themes: the loss of childhood innocence.

For example, the pilot dashes off a drawing of a box instead of a sheep, which the boy wanted. He feels a little guilty. But the little prince beams. He leans forward and says "Look! He has gone to sleep." Remembering this, the pilot observes: "But I, alas, do not know how to see sheep through the walls of boxes. Perhaps I am a little like the grown-ups. I have had to grow old."

The little prince tells the pilot about the planets he has visited and the people he has met, each one either offering a piece of wisdom or folly – sometimes both, as in the king who observes: "It is much more difficult to judge yourself than to judge others. If you succeed in judging yourself rightly, then you are indeed a man of true wisdom."

The list includes "a tippler", a businessman – of whom he asks "And what good does it do you to be rich?" – and a "lamplighter", whom the little prince thinks is the least ridiculous of them all "because he is thinking of something else besides himself".

Along the way there is a slightly pompous flower, a few talking roses that some scholars believe represent Saint-Exupéry's wife, plenty of volcanoes and a handful of baobab trees whose threat to the boy's planet has been compared to the growth of Nazism. It is nothing if not a surreal journey. But it is anchored every few pages by telling lines or observations, from James Dean's favourite ("It is only with the heart that one can see rightly; what is essential is invisible to the eye") to the exchange with the railway switchman which reads like a parable of modern working life. A passenger train rushes by, watched by the boy. "'They are in a great hurry,' said the little prince. 'What are they looking for?' 'Not even the locomotive engineer knows that,' said the switchman."

It is a book that has a special place in many people's hearts. "People who love this book absolutely adore it," says Tim Jones, publisher at Egmont UK which will celebrate the 70th anniversary with a new edition later this year. "It's a book I've always loved – when you meet people who feel the same way, it's like a shared secret. It sells phenomenally well, all on word of mouth. People use it as a life manual because of the wisdom in it. It's an established classic in French literature, part of the cultural fabric of the nation. I think it represents in French culture some of the things that Winnie the Pooh does in this country. It's one of a select handful of books that make you look at the world in a different way. It's a simple tale with a deeper philosophical meaning. I think that, particularly in hard times, people find comfort in these sort of stories."

Although a French classic, the book was written in Manhattan and New York State where Saint-Exupéry and his wife had fled following the fall of France in 1940. He was already an established aviator and author, having flown mail flights across North Africa in the 1930s and survived numerous accidents and adventures that form the basis of his novels Southern Mail and Night Flight, and his memoirs Wind, Sand, Sea and Stars.

He became famous for always carrying a notebook with him on his solitary flights, and using the time to read. Legend has it that he once circled an aerodrome for an hour before landing so he could finish the novel he was reading. He was a beatnik of the skies, a cloud philosopher who accumulated injuries from his numerous crashes, yet survived to take off again. One such crash saw him having to walk for five days in the Sahara before a Bedouin tribe came to his rescue. It is almost certain that he drew on this experience for The Little Prince.

He left the US in 1943 and joined the Free French Air Force, in Corsica, flying reconnaissance missions in support of the Allies. On July 31, 1944, he took to the skies but never returned, flying instead into mythology. His plane was not discovered by divers until 2000, and not raised from the seabed until 2003. His body has never been found.

Today, his estate is managed by his great nephew Olivier d'Agay, who has overseen a careful expansion of The Little Prince into one of the top 10 non-commercial brands in the world. "Its success is that it has a message beyond generations, beyond cultures," he says. "It uses universal language to carry humanist messages." D'Agay has allowed what he calls "a rebirth of the character outside the book", so there is now a range of carefully controlled merchandise, from stationery to tableware, clothes and toys. There is a website in seven languages and a Facebook page which has four million fans.

The little boy's message has spread around the world. He is an ambassador for the UN's Millennium goals and for various Unesco initiatives; there is a Museum of The Little Prince in Japan; and in South Korea there is Petite France, an imitation French village that uses elements of the story. The book has been adapted for an animated 3-D series in more than 100 countries and there is a TV series in France, with new stories based on the original. Over the years there have been many theatrical adaptations and in 2014 a movie will be released, directed by Mark Osborne, who directed Kung-Fu Panda.

Booksellers love it. Ros de la Hey at The Mainstreet Trading Company, in St Boswells in the Borders, says: "It's one of those books where you always have more than one edition in stock. We always keep a gift edition for a christening or special birthday." And Gill Macdonald at the Golden Hare in Edinburgh adds: "I love it. We have five copies at home. It's a book you can read again and again, and see more in it every time. It's wonderful."

In the UK, Egmont publishes The Little Prince (hbk £9.99, pbk £6.99). In the US, a 70th anniversary publishing programme launches next month with Houghton Mifflin publishing three new editions: The Little Prince 70th Anniversary boxed set, with an audio CD read by Viggo Mortensen; a new edition of The Little Prince with an introduction by Gregory Maguire; a new edition of the graphic novel by Joann Sfar; and an e-book version for tablets