but then I realized this video was better suited to another, earlier thread about being derivative in an original way:
You could argue that there are two distinctly British traditions of coming-of-age novels: the Arthurian (think the Sword in the Stone) and the school story. The best known example of the latter is Tom Brown's School Days; the best is Mike. Both genres are uniquely tied to British character and culture but, as far as I know, no one saw how fundamentally similar they were until Rowling came along.
You can see that underlying similarity of the two genres (and Rowling's skill at combining them) by imagining the Harry Potter and the Philosopher's Stone first with the fantasy elements removed, then with the public school elements removed. The results would be, respectively, a conventional school novel and a conventional juvenile fantasy novel, but they would both be basically the same story. Most of the characters and the majority of the plot work equally well in both genres.
To see connections between seemingly disparate elements and to find a way to bring them together in a coherent whole is pretty much the soul of originality, even those elements are old and familiar and worn smooth with use.