Listening to the audiobook for book 1 now, and the amount of dialogue and scene placement that is word-for-word the first season of the HBO series is extremely revealing. It demonstrates why the show has been so engrossing and highly regarded, and it shows why, not long after the show outpaced the books, the quality declined. The first season is barely an adaptation, it's more like transcription. It's clear that the show runners were entirely dependent on the books, not just for character and plot, but for every bit of metaphor, dialogue, pacing, and dramatic thrust. Like leaving training wheels on too long, by the time the show needed to be written around plot outlines instead of scene-for-scene, the writers weren't up to it.
I don't know for how many books this remains true. I know there is show material that is different, or more visual, than the books, and that editing decisions were made re: characters and plot, but it's clear that most of the magic of the show is from Martin. The show's final seasons deserved better than to be slapped together with explosions and callbacks.
It's not a disaster; I don't think it diminishes the impressive accomplishment of the show up through season 4 (or maybe 5?), nor should we discount the amazing casting, set design, costume, etc - all the elements of a quality *production* are there... It's just a shame to get a cliffs notes version for the end of these story threads. Absent Martin's writing, the show just has no verve.