Further to: the books being hard to read. While it's true you at times get inundated with a wall of names, places, backstory and events, (all of which must have taken years to dream up, write, and keep track of) you also get to read some of the most richly-nuanced writing ever written in recent times. And I don't say that lightly, being as I'm a writer myself.
Here's just a small example (from book 5):
Martin doesn't just tell you that the sun is setting on a cold snowy forest. Rather he puts it this way:
Night was falling fast. The shafts of sunlight had vanished when the last thin slice of the sun was swallowed beneath the western woods. The pink snow drifts were going white again, the color leaching out of them as the world darkened. The evening sky had turned the faded grey of an old cloak that had been washed too many times, and the first shy stars were coming out.
Then, in an earlier part of the same book, he describes what night felt like during a sea voyage:
Only the brightest stars were visible, all to the west. A dull red glow lit the sky to the northeast, the color of a blood bruise. Tyrion had never seen a bigger moon. Monstrous, swollen, it looked as if it had swallowed the sun and woken with a fever. Its twin, floating on the sea beyond the ship, shimmered red with every wave.
He doesn't just say what happened, he makes you
feel it and see it as if you were there. And that goes for basically every part of the story. You get to smell what the room or the swamp or the forest etc smells like, what the food tastes like, how it feels as the roar of a giant rumbles through you, etc.
You can tear through this story like it's a race to get to the finish, or you can stop once in a while and consider the words, the thought that went into the writing, and you'll begin to appreciate the sheer depth of this epic tale.