So i read some synopsis of events of the GoT series after season 2. No, i haven't watched it beyond that on account of actually reading the books and all and now i'm kinda glad i haven't because wow if the series isn't going completely off the rails in relation to the source material. Completely unnecessarily too, i might add. What on earth are the writers thinking?!

I think i'll just cherry pick the episodes with Brienne/Jamie/Arya/Everyone and everything north of the wall in it 
Oh, and good morning!
They kind of have to, considering the size of the cast. In the books, not everyone is going to be dead. To finish the show with a hundred characters is going to be quite chaotic and costly. In order to fix that, they do have to muck about with the character arcs, just a little. Don't introduce this character. Don't send this character over here. Et cetera. I'm not entirely happy about all the changes either, but I see why they have to be done, and admittedly, it's working. The show still feels fluid.
There is also the issue of moving into The Winds of Winter territory now so that's another reason why things might have to differ from the books.
Also, G.R.R.Martin kind of has a say in what happens with the show. He used to write an episode a season, but didn't for the last or maybe it's this season, can't remember. He seems happy with the show though, so it can't be all bad. 