Classic Mystery? Perhaps not. But here comes Harry VI:
Not classic? Not a mystery? I'd argue that the seven-volume series is, indeed, a very large but classic mystery (obviously with very strong supernatural and fantasy elements) - it is quite largely a whodunit with plenty of legitimate clues scattered throughout the seven volumes, along with a myriad of very red herrings. It is about Harry's search for the truth. In that sense, it follows the pattern of Classic Mysteries.
Besides, it's MY blog. So enjoy... ;-)