What are the motifs in Arkham Asylum by Grant Morrison?

The recurring idea has to do with heroes and villains. Batman is a traditional superhero, while the Joker is his arch-nemesis, a traditional super villain. However, in this story, the hero, Batman, must examine his inner self for demons worse than any external villain. The Joker becomes Batman's guide through his own psychological process instead of a traditional villain. The line between hero and villain is blurred. The same ambiguity of hero and villain is present in the story of Amadeus Arkham.