I came across a book recently (the name of which I've forgotten) which was about re-reading the books you had on your shelves. The author had spent a year going back through the books in her home instead of buying or borrowing new ones. (I wrote about this somewhere else, but have forgotten that too!)
I doubt if I could commit to a year of only re-reading (the library is far too close to my workplace for that to happen) but I think some re-reading is a good idea. Not entirely as a result of this (perhaps more because I watched the DVD of Harry Potter and the Half-Blood Prince the other day - and was only slightly more impressed the second time around than I had been at the cinema) I began to re-read the Half-Blood Prince again.
Not surprisingly, it's far more detailed than the movie - the latter chops characters and incidents out on every side - and I was kind of pleased to have it confirmed that one particular scene in the movie hadn't been in the book at all - the one where the Weasly's house is attacked by death eaters and then burnt - because I remembered thinking both at the cinema and while watching the DVD that it wasn't part of the story. I'm not entirely sure what it's doing in the movie at all, except perhaps to reintroduce some of the characters. As a scene it doesn't entirely work in plot terms (Harry would probably be annihilated, as would Ginny, when they run out in the marshes). In cinematic terms, of course, it's fine.
However, I was surprised to find that the book turned out to be less-well written than I'd remembered. It lacks the quality of the writing that made me stop at the corner of Filleul St and St Andrew St after I'd bought the first Harry Potter book a decade or so ago and just read. Here the language and style is rather more prosaic, especially when dealing with some minor characters. The main actors in the story still have their individual voices, pretty much, and Voldemort as the child and teenager is as appallingly scary in the book as he was in the movie (both the boys played him very well), but some other scenes are just there. They have a feeling of being written, but not written with much passion.
That aside, I still found it worth reading again; there are some great set-pieces, and the gradual unfolding of the plot (which of course happens at a much slower pace than in the movie) allows things room to breathe - perhaps a bit too much room (especially when it comes to the snogging), but that's okay. Rowling's world became so full after a while, it was a bit as though she wanted everyone to enjoy it as much as she did.
In consequence I'm now re-reading the last in the series (Deathly Hallows). This opens with a lot more energy, and after several chapters that same energy remains. Hopefully that's the case throughout.
I haven't read this since it first came out back in 2007 - we ordered copies in England while we were there, and had it delivered to our door the day it was released - so once again I've forgotten a huge amount of it. It's very dark, naturally, and it's going to get darker. But man, it's a page-turner! I've only one quibble. There are now so many characters that you virtually need a name dictionary to keep up with who's who.