The story has diverged enough in certain respects that even book readers with great memories can't be absolutely sure of exactly what's going to happen. For example the Sansa/Baelish subplot this episode changed Sansa's role in a very important respect from the book, with many people, including me, thinking the way it transpired on TV was better. The Missandei/Worm story doesn't even exist in the book, and it's lovely, though perhaps not essential to the entire series arc. The way I see it, sheer page volume aside, the internal struggles of characters plays such a large role in Martin's writing that they have to find other ways to advance the story on screen. In some cases just removing entire scenes, in some cases resorting to clunky exposition, and in many cases attempting to translate the general tenor of the written page into a new scene which may create, combine or transpose characters and locations. It's not always successful but when it works it adds a new dimension to the story, like an elaborate cutscene on a DVD.
I also liked some of the cinematic storytelling devices the director employed, for example, in a couple of scenes having direct questions go unanswered on screen, which tends to be used more in "serious" film than on TV. Or the juxtaposition of seeing an Ironborn warrior go immediately from alive to gruesomely dead. A kind of gallows humor, but deadly serious in portraying the stark immediacy of Ramsay's treachery and cunning.