I had two false starts into A Game of Thrones before I started reading the entire series. Being a fan of epic fantasy, I've always enjoyed Wheel of Time and LoTR style magic and world building. A Game of Thrones was my first foray into Grimdark. It quickly took hold of me and wouldn't let go. From the moment when young Brandon Stark was pushed out of a window by a much older man to prevent the leaking of a truly embarrassing as well as shameful truth, I knew I was in for surprise galore. The series has far more surprises and unexpected plot twists than is the norm for fantasy.
The characters were simply marvelous. Nearly everyone who's read the series initially rooted for Ned Stark. I wasn't an exception. The constant killing off of main characters is a theme that is unique to this series. At some point, I stopped rooting for anyone, although I still have some favourites. With the vast array of characters, keeping up with the story can be a bit difficult. But I love these kinds of challenges! Besides, the tight-knotted, heart pounding suspense in the series is enough to make one persist. The characters are of every possible type. There are noble-hearted lords, incestuous twins, black hearted killers, dumb daughters of noblemen, power hungry lords and their ambitious underlings. There is a fire immune dragon lord (or lady), numerous usurpers, conniving double hearted bastards, amongst other people. It makes for an extremely unique reading experience.
The setting is just top class. These days, writers don't do so much of world-building. They'd rather just jump in. The gradual easing of readers into the world is so expertly done you're sucked in without even knowing.
The storyline is the best part. The uniqueness, the relative lack of magic, coupled with the freedom given the characters by the author makes for a truly fresh, original and unique reading experience. It's fantasy, but it is also an accurate reflection of the wide range of the human character. It's an expository on the nature of man.
I do hope Martin doesn't die before finishing the series. It's simply unique!
Did I forget to add? The series is filled with numerous quotes and heavy punchlines!