I'll give you that the first season was closer to the books than this season has been. And I apologize for the spoilers and hope I didn't ruin anything for anyone. No spoiler tags here so I did what I could.
Problem is, if they followed the book to the letter, I think the show would be quite boring to watch in comparison. It would be too slow and drawn out.
Granted there are changes, but to be honest I think the adaptations had to be done to keep it watchable. And the reality is, the viewer numbers agree

Though the proespect of waiting a whole year for the next series isn't fun
