Is the upcoming show A Game of Thrones based only on the first book or the entire series?

I'm nearly finished with the first book and was wondering if I need to hurry to finish the other which are out in time for the show to begin or if the TV show is based only on the first novel.Is the upcoming show A Game of Thrones based only on the first book or the entire series?
It's going to follow multiple story lines of the series closely, but that's throughout the seasons planned. But it's going to be very faithful to the series and there may be spoilers, but there also will probably be sections of it that are unseen in the book added in to give more action and depth and turn the show into something more like a show and less like a miniseries or book, use True Blood as an example of what I expect it will loosely turn out to look like. I bought the books for my dad's birthday in August, and then we started seeing trailers for it and now he cannot wait for April. Is the book really that good?