Why did Paula Coehlo use this reference to Narcissus at the beginning of the book?

The Alchemist, a character who will not be introduced until much later in the narrative, finds a book that retells the myth of Narcissus. The myth of Narcissus traditionally tells how a youth, whose name was Narcissus, loved his own image so much that he spent days looking at his own reflection in a lake. One day, he was so infatuated with himself that he lost his concentration, slipped and drowned in the lake. A flower grew by where he fell and this plant came to be called the narcissus.

The author of the book the Alchemist finds is different, though. It continues by telling how the goddess of the forest went to the lake after Narcissus had died and found it converted into a lake of tears; the lake was weeping for Narcissus. The lake missed Narcissus because, in the reflection of his eyes, the lake could contemplate itself. This version of the myth makes the Alchemist very happy.