I'm working my way through a borrowed copy of Harry Potter and the Half-Blood Prince, and I say 'working' my way through it because (as of page 294 so far) I'm finding it, well, kind of tedious. I feel like this makes me some kind of heretic, but I'm just not enjoying it very much. There's nothing particularly wrong with it, but at nearly 300 pages in there just doesn't seem to be much going on that's holding my interest.
I have also read the other 5 books, and while I quite enjoyed them, as an adult reader I haven't been swept up in all the fuss surrounding the series. I have, however, found the books to be quite entertaining and diverting reads - just not exciting.
What I do think is absolutely fantastic about these books, is how excited children are about them. Anything that gets kids excited about reading, and so excited that they would sit down and read a whopping great book in a single sitting or re-read them several times, is just fine by me.