I'm aware of how the adaptation process works and the constraints of the TV show, but what they have adapted is crap. Sure, I'm a book snob about certain things and there are plenty of nitpicks, but the bottom line is... Game of Thrones isn't a good show. It's stupidly popular, but then so are the Kardashians. HBO have taken an epic fantasy saga, rich in lore and complex characters and turned it into poorly written schlock devoid of any nuance of understanding of the source material. And that's fine for your average TV viewer because they don't have the reference point and don't know any better. As long there's enough cheap shocks and titties on screen, then nothing else matters!
As for GRRM's approval, he's had less and less involvement on the show. I don't think he's even written an episode since Season 4. I've even heard that he's made a few ambiguous comments on his blog about the direction of the show. Although that's more fool him for selling out when he knew he was never going to finish the books in time. Not that his bank balance is hurting for it.