Just curious, are the upcoming books expected to go in the same direction that the TV show is heading? Or could it be a totally different conclusion? I haven't read the books, and I a don't know how accurately the show has been following the books. I am just wondering whether there is any point of reading the books after seeing the show.
An illustration here comparing the books vs TV seasons should help:
S1 one was a near perfect adaption. In fact they actually had about an hour of room left to film, so they improvised a lot of those scenes where it was just 2-3 characters in a room talking. Book 2 is a good bit bigger than book 1 and wasn't going to fit into 10 episodes, so they tinkered a good bit more but it's still relatively close. Book 3 was also slightly bigger than book 2 but it's the corner stone of the series up to this point, so they devoted to full seasons to 3+4 it with a little bit of spillover into book 4.
Books 4 and 5 were only intended to be one book, but it was getting too big and unwieldly so GRRM had to split it into two books that actually ran parallel to each other. Pissed off a lot of fans because Jon/Dany/Tyrion and a few others weren't in book 4, so we were left hanging for over 5 years.
Regardless, there was no way to properly adapt these monsters to the show so it's gone way off course. It's where a lot of criticism comes from, while in Feast (b4) GRRM devotes just as much time & detail to Dorne or the Iron Islanders as he does the rest of Westeros, D&D have only a few segments of room to come up with an improvised story and it falls flat... not sure how much you can really blame them though as it's not an easy task.
About the only thing I feel the show has definitely 'spoiled' for me as a reader was the "hold the door" moment and the birth of the Night King/origin of the white walkers. With everything else it's either gotten far too different in the show or is so much more complex that I'm not at all worried.
One simple example that I would consider an inconsequential spoiler, is that Sansa never left the Vale for Winterfell. One of Sansa's friends survived the butchering in season 1 after Ned failed to secure the Throne, and with no one actually knowing WTF happened to Arya the Lannisters are claiming this is her. It's why the Bolton's needed Theon so badly for the wedding, to validate for the other Northern lords that 'Fake Arya' (actually the former Stewards daughter) is the real Arya.