I couldn't possibly give you a summary without spoilers, but I can give you the general set-up:
In the kingdom of Westeros, noble families are constantly vying for power and for the throne--including the scheming Lannisters, the stoic Starks, and the ambitious exiled children of the former ruling family, the Targaryens. The previous generation saw a war that overturned 9and killed most of) the Targaryen's mad dynasty, and though the kingdom would seem stable, there are far more plots, schemes, secrets and betrayals going on than you can imagine.
And meanwhile, something is stirring on the other side of the immense man-made ice Wall in the North...