I'd say even just start with the most recent season since they pick themes that can be found or read from the HP books and discusses what those themes are, their history, and how they are found in the books.
For me, it meant more that I read them and experienced them with people than that I read them, so that's something she-who-must-not-be-named cannot take away and it's also something that can't really be recaptured either.
Is book 4 the one with the triwizard tournament? I missed that aspect of fandom because I read book the triwizard book in direct anticipation of the release of the next one.
yeah i definitely can't blame her, she's very popular in some circles so she already deals with an absolute avalanche of idiots telling her that she's doing this or that wrong