By volume three (Prisoner of Azkaban) and four (Goblet of Fire) it started to seriously fail as a read-aloud. For readers who might have jumped into the series late, Rowling had to repeatedly recapituate what what happened in #1 and #2, which does slog things down, and then Rowling starts jerking the reader around with plot-twists that I think abuse the younger readers'sense of continuity of character.
By #7, Rowling actually discards the rules of her own "sub-creation" (to use Tolkien's idea) and lets her main characters do things which are against the foundational laws of morality of her own fictional world. Specifically, Dumbledore colludes with Snape in his own death (which is either suicide or murder), Good guys use two of the Unforgivable Curses (Minerva uses the Imperius and Harry uses Cruciatus) and, if I remember rightly, these violations are treated as having no significance whatsoever.
That's the problem, to my mind. They use use the Unforgivable Curses almost casually, as if there were nothing very remarkable about it. No internal or external debate about it beforehand, no complications of conscience or consequence afterwards.
I'm not so simple-minded that I think Good Guys can't do Bad Things, but in the fictional/mythical world --- just as in our own world --- Bad things remain implacably, inescapably Bad, and have their tragic consequences. But in the book, Dumbledore's death at the hands of Snape (morally wrong, and one could say, even worse, mythically wrong) and Harry and Minerva's use of Unforgivable Curses never even get a rebuke, still less a consequence.
I don't think this is nit-picking. I think Rowling is effectively giving the message that if you're on the Good Side, you can do whatever seems necessary; even if it's evil for others, it's not evil for you; and the evil does not corrupt you.
Now, that's a troubling message.
I wouldn't read these books again.
Thanks for your critical comments. I agree with them; I was astounded to hear my Jewish sister say that Harry Potter was supposed to be a Christ figure, because I didn’t see him that way, but thinking about it, she was correct.