Lots of people say that reading the books first was better, but honestly I'm not the biggest book reader and I enjoy a good show compared to book (usually).
I'm glad I watched GoT before I got into the books. The show is amazeballs and I was craving the plot so much after each season, so the books filled that gap nicely while I waited for the next one to begin. Problem now is that I've read all the books and numbnuts takes a decade to release a new one so there's not much left in between for my fix.
Would be sick if all 4 spinoffs were picked up and we had an all year GoT orgy. There's certainly enough demand for it.