What @ill said.
It's basically a historical timeline going back to Aegon the Conqueror and stretching to the present (I think in that book the "present" is basically Robert's Rebellion).
Some factiods, history of internal struggles within the family tree, etc.
It gives details on war, deaths, etc, but as far as building a show off that material it gives the foundations of the storyline but doesn't give much in the way of character building, motives, etc. If the showrunners are good (and not D&D), then they can make a hell of a show out of it, particularly the Dance of Dragons section which Hot D is based off.
