The books are progressively getting better, although I did only embark on reading them in Latin because of a course I was involved in.
The movies are getting pretty awesome now, too. The last one was quite excellent, and the one prior to that was directed by the same fellow that done Children of Men, so it holds plenty of aesthetic value - even if the story-lines had not gotten interestingly dark and complex enough by then.
One of the most interesting things about the Harry Potter books is that they happen in *real* time. I.E. Rowling has altered the tone and storylines as the audience has grown up - it's a literary phenomenon. Probably deservedly so, too.