Nice title, eh? Unfortunately I don't have the answer to why Harry Potter is such a raging success. You can be sure of that because if I did have the answer I would be making the best of it, writing wildly successful books, and giving J.K. a run for her money. (I know, cheeky of me to think that I could, right?) I can, like Rasberry, only give my musing thoughts on the subject.
The first lesson I would want to take from Rowling is how to get my writing to appeal to both children and adults. I suppose part of the success could stem from her use of such universal themes and identifiable characters and situations. Good vs. evil, the importance of friendship, the qualities of courage, the list goes on. I know that I love Harry Potter because it tells the stories we never get sick of hearing, even after we've grown up.
And creativity! The books are bursting at the seams with a unique and colorful world where everything is a new discovery, not just for the main character, but for the reader as well.
I also believe that Rowling has mastered the art of literary hooks. Each book is driven forward by a sequence of mysteries and often the solving of one is the discovery of another. I think Rowling has also found value in people's love of speculation. Readers like to make guesses about plot lines, they love to be proven right, and they are down right ecstatic when they are proven wrong by some brilliant plot twist they never saw coming. They key, then, is to lead them to speculate. Unfortunately the key to that key, writing a "speculatable" novel, is beyond me.
I could prattle on about different aspects of the books that draw me in, the heroes I love to love, the villains I love to hate, the interactions with their huge build ups and awesome payoffs, and of course my love of all things British, but those are all the little things that appeal to my particular tastes. So maybe it is as Rasberry says, the books simply have enough little things to appeal to a large audience.