The genius behind J.K. Rowling's Harry Potter series is manifold and delightful. In the creation of a wondrous world, we meet a downtrodden but victorious sympathetic hero -- an orphan in the Dickensian tradition. Harry Potter starts out a lonely, goodhearted, courageous boy who is learning his true calling on his journey of growing up. The series uses the timeless morals of good (Harry and Professor Dumbledore) triumphing over evil (Lord Voldemort & the Death-Eaters); open-mindedness (the Weasleys), winning over ignorance (the Dursleys). There are also those themes essential to young adult literature: finding one's identity, and the theme of children on their own. The smooth writing style also makes these books an enjoyable read for all.
At series start, Potter's genial good nature and kindness to others amasses him friendships that later come in very handy in a pinch, for example, when Harry was being saved by the timely aid of Hagrid the gamesmaster, Dobby the House Elf, and the ghosts Nearly Headless Nick and Moaning Myrtle. But Harry has no motive behind his kindnesses save compassion and doing right; it's in his nature.
In the Hogwart's School of Wizardry, each book brews plots of supernatural trouble (generated by the Dark Lord and his followers) that threaten not only the school's but the wizardry world's existence. But then -- unwittingly and almost unwillingly -- Potter comes to the rescue. Because he's a good person and cares about others, and will work to save people at all costs, he always acts heroically and does the right thing instinctually.
As social satire, I can't help but marvel and laugh: the send-up of the civil service, the way class snobbery is dealt with especially with regard to the Ministry of Magic and the awful people who run it. But, just when you think a character is all bad (or all good), Rowling turns the tables and shows how people, even magical ones, have many facets indeed. The plot, characters, and theme all start to come together as the writing progresses as part of the writer's journey. Harry Potter books work on many levels: psychological, moral, spiritual and as social satire. Their genius lies in their wonderful plots, vivid characters, and how much fun they are. Small wonder they're so popular.
Even though Harry, growing up, isn't quite as adorably likeable to either his friends and family or us, the readers, we sympathize with him because, growing up is tough! Harry definitely has issues... his anger and confusion are coming to the fore, and they're not pretty.
Harry Potter books also have the power to stoke (or engender) Anglophilia. England (and the Potter world) has a strict social class and lineage system, hence the constant comparison of the rich and snobby Malfoys contrasted against the humble but accepting Weasleys -- both "purebloods," but the Weasleys aren't bothered by wizards of non-pure blood. Besides, often the "pureblood" wizards are often pitted against muggle-born or "mudbloods". Although unrelated really to the theme of the journey, these sorts of distinctions mark the Potter books as seeming peculiarly English.
The series opens with Harry Potter, at the (magical) age of 11. An adopted, abused orphan, Harry lives with an aunt, uncle and cousin who are almost unbelievably mean-spirited and stupid -- and who mistreat Harry constantly. A godsend comes in the form of an invitation to the Hogwart's School of Wizardry -- the place where he belongs. But along this journey of discovering who he is, who his parents were, and what his purpose in life might be, almost everybody recognizes "the famous Harry Potter" as a miraculous survivor of a terrible dark wizard's wrath. Lord Voldemort disappeared for eleven years but keeps trying to return -- mostly so that he can obliterate the last Potter, Harry.
Not only is Harry famous, he was left a small fortune in the wizard's bank, Gringott's, by his murdered parents. Even though Harry would have done anything to prevent their murder, live as a normal family with them and not be a famous and independently wealthy young man, his destiny is otherwise, and as the ancient Chinese curse goes, he lives in interesting times.