Surely Bloom is a bit harsh on Rowling? I don't know. I am a literature graduate, and although far from an expert, I do appreciate and regonise 'great' literature, Miller included.
But, looking at Rowling, this is someone who - through words - has created a world that people from nine to ninety have grown to love, and empathize with, and think about beyond the last page. Perhaps the fact that Rowling has done that with cliches and dead metaphors should be a note to her credit, and not something to sneer at.
In this article
here Bloom is quoted as saying that great literature should "To enrich mind or spirit or personality". I think Potter does that.