Meereen: The second siege of Meereen is inspired by the novels, although it has come at a somewhat different point in time and seems set to be resolved much more quickly.
Riverrun: A deal of the dialog is from the novels, although with some significant changes. So, too, is Edmure handing Riverrun to the Lannisters, but also with some very significant changes.
Possible Developments in Future Books
Braavos: Arya escaping the Faceless Men through violence cannot be ruled out at this time, although the show’s particular path seems motivated by the constraints of the show’s timeline.
The Riverlands: It’s possible that if something were to happen to the brothers at the Quiet Isle, that Sandor Clegane—the gravedigger Brienne sees but does not recognize—might go on a quest for vengeance, but it’s unclear that that’s the direction the narrative is going in the novels.
Meereen: It seems possible that Daenerys will ultimately intervene with Drogon in the second siege of Meereen.
King’s Landing: It can’t be ruled out that the High Sparrow might somehow maneuver matters to force Cersei to not be able to depend on a trial by combat (with Ser Robert Strong as her champion)... but it seems very unlikely that Mace Tyrell, as Hand, would permit that to happen all considered.
The Riverlands: The Brotherhood without Banners turns darker in A Storm of Swords and after, but their focus is single-mindedly on killing Freys, Lannisters, and their supporters under the leadership of Lady Stoneheart following Beric giving his life to resurrect her. With Beric still alive, the brotherhood is taking a very different course—northward, apparently—which is not part of their story in the novels.
Meereen: Varys is not in Meereen in the novels, and is unlikely to ever be, much less going there and then returning to Westeros to look for allies.
King’s Landing: Kevan’s attitude towards Cersei is far more hostile on the show than in the novels. While in the books he is aware of her shortcomings and opposes her having any real control over the realm, he’s acutely aware of the importance of getting her out from under the High Septon’s thumb. His apparent glee in seeing her trial by combat denied is quite a change, as in the novel he supports the idea (if uneasily) of Ser Robert Strong championing her.
Riverrun: Jaime’s attitude towards Cersei—complete devotion—is very different from where things stand in the novels, but this is in large part due to the massive changes to Cersei’s character in the show. However, Edmure giving up the Blackfish is a radical change from the novel, where he facilitated his uncle’s escape, and there’s simply no reason whatsoever that Edmure in the show would make a different decision beyond the fact that they writers decided they wanted Edmure to act differently. It’s one of the more egregious changes. Had Edmure offered to let the Blackfish escape and Ser Brynden again saying he’d rather go out fighting in his home—because the situation for the Blackfish is a bit different than in the novels—it would have fit better. Finally, while Brienne and Jaime do meet in the riverlands, it’s not at Riverrun and circumstances are very different for both characters.
Braavos: The waif’s personal vendetta against Arya is not a factor in the novels, so even if Arya leaves the Faceless Men under bad terms the narrative will be driven in some very different fashion.