Possibly my favorite passages/sequences, of all the books, is the chapters leading to the siege of winterfell.
Mance Rayder's duplicity, the Northern Houses quarrels, Roose Bolton's growing impatience, Reek's transformation to Theon, Ramsay's slow unhinging, the torture of Jeyne, Stannis's death march through the snow, the Iron Banks late arrival, Theons escape, the Pink Letter.
It interweaved and connected to create a hypnotic spell of horror and from the page it felt almost transparent, gothic and ephemeral, truth hidden within the snowstorm.
As a reader you were never sure what was happening exactly, how each strand would come together, the water drip building of pressure and the escalating feeling of dread was GRMM at his most masterful.
Now, i would not expect the tv series to rise to the same heights and necessary simplifications need to be made, but the thought they may fail to capture the essential dread and horror is hollow... Rayder already dead ?, Sansa replacing Jeyne, Littlefinger involved...?
To carve up one of the books greatest parts and replace it with Xena Snakes, Cersei & Jamie's squabbling and Tyrion & Vary's jolly roadtrip...mmm well.
Hoping to be wrong !