I don't think I'm qualified to have an opinion on the matter, but I've heard it said that writing "The Little Prince" qualified Antoine de Saint-Exupéry as one of the greats of the existentialist philosophy movement.
I have some vague memory of reading the story in English when I was a teenager — as part of a literature class. I wondered at the time why a little picture book meant for small children should be considered literature. I thought the story was cute but not very profound.
I didn't read it again for decades, and then I only did so because I was studying French. "The Little Prince" is baked into francophone culture. If you quote a line like, "Dessine-moi un mouton," draw me a sheep, French speakers immediately know what you're quoting.
So, it seemed to me that if I wanted to truly understand French, I had better add Saint-Exupéry to my list of must-reads. I started with some of his adult aviation adventures. Before World War II, he was a pilot in South America, and he wrote some spine-tingling tales based on his experiences.
I liked the stories, but I didn't LOVE them. He clearly had a knack for lyrical writing, but he didn't indulge it very often. His early writing is very much story-forward and action oriented, fascinating perhaps for those interested in the early days of aviation, but only rarely showing poetic or philosophical promise.
Then, finally, at the insistence of a friend, I picked up "Le Petit Prince" and read it slowly, with attention. Then I read it again. And again. And again.
I laughed, shed tears, and found my imagination sharing a tiny cockpit with a daring pilot carrying mail for disinterested recipients who would never know the risks he took. His dangerous night flights led him to ponder the nature and purpose of a cold, disinterested universe. Then he produced a sparkling gem of poetic philosophy wrapped up as a charming story for little children.
And then he died, unremarked by the disinterested universe he wrote about, but increasingly loved by people who share that same universe — increasingly remembered and cherished.
It's fitting, really, that his personal story shines from inside his most famous story.