Wow wow wow, hang on just a second there, hold on your horses.
HARRY POTTER is certainly NOT one of the best work of literature ever written. The fact that it has been popular is mainly because of a solid marketing startegy and a story that seems to reach out into people's imaginations.
The style of writing, the narration, the plot, the figures of speech, everything about it is fairly simple. True, there is a certain je-ne-sais-quoi about simplicity, but it most certainly is not a telltale sign of greatness

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I should have said it is one of the best works of literature I have read.