Did you happen to see Pillars of the Earth based on Ken Follet's novel of the same name on Starz? That stuck close to the book, but felt rushed and different.
Then there's True Blood on HBO, which stuck close to the first Sookie Stackhouse book for the first season, swayed away in the second, and only used the book as a base in the third season.
I say all that to say that I haven't read the books Game of Thrones is based on, and I'm glad I haven't. I'm so intrigued by the show that I want to, but I find reading the books after seeing the movie or show is better than the opposite.