Do you feel the show is now spoiling plotlines that we didn't even know existed, as of yet in the books? I'm specifically referring to arya's storyline but i'll get to it in a minute. TLDR is at the bottom.
Caveats: The show is an adaptation, though some may feel it's a veryloseadaptation, based on the storylines of the existing novels, the framework given to them for upcoming novels, and the ultimate conclusion told to the show runners by grrm for each of the main players. The paths they take to get there will not be identical, and because of the medium there are various restraints (like actors, time constraints, financial concerns, settings, etc) which will result in further changes, either planned or sometimes unforeseen changes from the book to the screen. These issues compound season after season so eventually the storylines may become wildly different than how they appeared in the novels, but ultimately the same outcome occurs.
Since George elected not to use the 5 year gap, the last few novels have mostly just been filler to pass time before the main characters complete their training montages. Shit happens, side characters are introduced, sometimes it's interesting, and some events may even be relevant later, but mostly it's just filler.
Books 1 -3 set up every single character with approx 5 years of downtime, whether it's learning to command (jon), learning to rule (Dany), learning to be a maester (sam), learning to fight left handed (Jaime), learning to play the game (Sansa), getting over grief and regret (Tyrion) etc, etc, etc. With this knowledge, we all kinda assume that Arya's 5 year gap "downtime" is her training to become a faceless man, so that she can return to westeros and kill people. Without the 5 year gap, we've gotten to read about this journey for the last 2 books, and watch it unfold for the last 2 seasons, and thus it seems like it's quite an investment, and thus deserving of some huge payoff, which would be true if it wasn't just filler.
But now, shit has started to go sideways for Arya in the show, which has raised a lot of questions in the TV thread (along with about 6 pages of shit slinging between retards arguing over the metaphysical aspects of how face changing works). The common thread of the questions is this:
"Wait, how is arya going to become a faceless man now? I mean that's how it's going to happen in the books"
But is it? how do we know that?
Of course there's a few episodes left of the season and we don't know how it will end, but it seems most people are coming from the perspective that Arya completes her training, or at least learns the magic needed to become a faceless man, and then returns to westeros. So all the theories and speculation surrounding the current situation are trying to maintain those prerequisites, and those theories are becoming more and more absurd. Otherwise, people just assume that it's "yet another change because TV, it won't happen that way in the books"
But when we compare her show story with her book story, and see the similarities, the same failings and faults that book arya has being shown in TV, it becomes apparent to me that perhaps the show isn't changing the book storyline, it's spoiling the book storyline that we didn't even realize could occur.
Book Arya is in the house of black and white, training to become a faceless man, same as TV arya. There have been some changes and some abbreviations of the story due to TV restraints of course, but the major elements of the storylines are the same.
Just like Show Arya, Book Arya isn't really buying in to the whole "becoming no one" which is a requirement to becoming a faceless. In the books she cheats at the blind fighting trial by warging into a Cat and seeing through it's eyes to "pass". We also know her thoughts because it's a book and can read her internal monologues, she's definitely still Arya.
In the books she completes her first assassination of the insurance man without a problem, while in the show she bails on that assignment when a person on her list (Meryn Trant) appears and she decides she'd rather scratch his name off her list instead. But in a way, she does the same thing in the books. In Arya 1 preview chapter of Winds, she's on assignment with the mummers doing the "war of the five kings" play, called "The bloody hand" (more on this in a minute), and risks failing that assignment when she notices Raff the sweetling in the audience and decides she'd rather scratch his name off her list. (The show had already used this kill back in Season 4 at the Inn with the hound, so changed it to Meryn Trant dying instead). We don't know the fallout from this choice, everyone just assumes she's fine and gets away with it...
So what do we know of Arya in Winds? We know the faceless men have sent her on a mission to kill someone, but we don't know who it is yet. We know she's infiltrated a group of mummers, which is the same as the TV Arya.
Now since the show is so far ahead of the books, we see that (atleast TV) Arya's mission is to assassinate an innocent woman because of a greedy understudy... and while infiltrating these people, getting to know and empathize with them, she realizes that the faceless aren't what she was expecting, they are a death cult, religious assassins, who serve death, they care not for innocence or guilt, only that they appease their god by granting death (and perhaps they kill for money, there are no specifics in how one pays for their services), and she decides she is Arya Stark after all.
TLDR: Before the show, the assumption was that Arya becomes a faceless man and returns to westeros. Now the show is questioning this assumption, and my belief is that this is more than just "durr show makes changes all the time, it's not going to happen like that in the books, she'll totally become a faceless man"
It's possible she dies in braavos, and that's the conclusion of her story. Or, perhaps she does survive, and returns to westeros as Arya, and not a faceless no one. Hell, perhaps in her moment of death she enters the wolf dream she's constantly having, ie wargs, and becomes Nymeria, living out her days murdering all with a great wolf pack at her side (nah not really, but it's possible).