Mereen played out exactly as one would have expected. No surprises there, but still satisfying.
I suspect that the show has diverged so far from the books that this episode's action will not have much in the way of spoilers for book readers. Certainly the battle of Winterfell will play out very differently. I expect the Manderlys, who played no part I know of in the show, will be the critical actors in the book. I still expect Stannis to survive, and hope for him to become Lord Commander of the Night's Watch, if there is such a thing in the future.
I still keep some hope alive for Rickon. There are many dead show characters who are still alive and more or less well in the books.
Lots more detail and excellent analysis in the vid.