I bought this book on the strength of previous reviews and am pleased to say I was not disappointed. As has been stated, GRRM's style is one of multiple viewpoints (initially confusing although by the middle of the book you know who's who, and in which 'house' they belong), within a continuous time thread. The writing is dark, gritty, and melancholic.
This isn't a 'quest' book; more of a history. And a realistic one at that. Although there is a complete lack of elves, dwarves, orcs, goblins etc, this book should be classed as high fantasy. Dragons, monsters, and magic exist in this world but they are relegated to the background. Nine tenths of this book deals in the down to earth machinations of the various courts. Heroes and villains do not exist. Everyone is painted in shades of grey. (Some greyer than others).
In the last 20 years there have been two books that completely blew me away. The first was Magician by Raymond E Feist, the second was Assassin's Apprentice by Robin Hobb. A Game of Thrones is the third. If you enjoyed either of the first two you will surely enjoy this.
Having read the rest of the books in the Song of Fire and Ice sequence, I can reassure you the standards set by A Game of Thrones are maintained.