looking for a philosophical, get to know/find yourself book for a traveller

A good friend traveled across asia and Australia for the past two years and has seen many different cultures. Lately we casualy talked about books and how he began to like reading. He also dropped a famous author, who is known for "Important life lessons" or "get to know yourself better" books. But not the spiritual, esoteric nor religious kind of books, but more naturally themed with Important life lessons and thoughts (idk how to describe it better). Does someone know any famous authors or can suggest a good author/book about it? It wasn't culture specific, but If you think, it might be worth, please suggest it anyway.