The Adventures of Huckleberry Finn is often referred to as the embodiment of mythological characteristics.

I think the mythology simply comes from the mythic archetypes that Twain uses. Huck is our hero with his call to adventure. He goes through the classic steps of the hero's journey beginning with answering the call and floating down the river. Huck has a sidekick and mentor figure in Jim, atonement with father (well he's dead) and many trials along the road. We can follow Huck through his adventure all the way to the end of the story where, with the freedom of Jim, Huck realizes his quest.