George R.R. Martin is taking his time finishing writing the books for the Game of Thrones series. So the writers had to pretty much come up with their own stories in the later seasons which includes the upcoming season 8 which will officially end the series on TV.
So what you see in the ending of the series might actually differ from the book. If it ever gets finished. This news was revealed by Martin in a recent interview with Entertainment Weekly where he said, “I haven’t read the [final-season] scripts and haven’t been able to visit the set because I’ve been working on Winds. I know some of the things. But there’s a lot of minor-character [arcs] they’ll be coming up with on their own. And, of course, they passed me several years ago. There may be important discrepancies.”
The HBO showrunners have also confirmed this, saying that there will be parts of the series which differ from the books, but they will not be telling viewers what those differences are so that they can find out for themselves when they read it.
Martin also says, “It’s been an incredible ride. And almost all of it has been great. Obviously, I wished I finished these books sooner so the show hadn’t gotten ahead of me. I never anticipated that.”