I've read them all and love them. The movies are always a let down as they never follow the story exactly and leave out bits that I think are crucial, but that's me. My dad actually was the one that got me into them oddly enough.
The only problem with them is that as Harry is growing up and having to face more grown up situations, the books are less appropriate for younger readers, and therefore, so are the movies. I would never have taken say a 4 year old to the third movie, but people did, and they had to leave with bawling child in tow (pet peeve of mine, bringing young children to graphic movies). People assume that all the books and therefore movies, are fine for any age of child (they somehow miss the PG-13 rating???). But that's a whole different topic, don't want to get off topic.
As Erised brought up, the books have taken on a real dark tone since book 4, but I think there's a reason for that. Harry IS growing up and facing grown up challenges, which are not always happy hunky-dory times. Its extreme yes, but a reflection of the turmoil teens face. Okay, maybe I'm reading too much into it and the author is just going through a dark phase herself, who knows. But for me, the dark tone adds to the story. Change is good. If a series follows the same tone and path in every book, then every book starts to read the same, they start to blend together. This sudden change in tone sets the second half of the series apart from the first, and sort of brings in a whole new level of readers. I'd say that books 1-3 are for the younger readers, readers that would be around the age of the books' characters, and books 4-6 are for the older set, again following the age of the characters. B)
