In the fantasy land of Westeros, summers and winters can last years. There used to be dragons. Beyond the Wall, there is talk of giants. Magic? There's a bit of magic still left. And then there are the Others, mythical beasties thought not to exist. The elements of fantasy I've described here are what allow the book to be classified as fantasy: in fact, the real story is more historical fiction modeled after medieval Europe. It is, after all, a game of thrones, and the throne is made of iron.
One of many brilliant things about the book is that Martin tells the story through POV chapters. Now, telling a story through the POVs of different characters is certainly not new; I probably first encountered the technique in Richie Tankersley Cusick's The Lifeguard. But Martin really plays with perspectives. Sometimes he will show the reader a scene from the point of a view of a child who does not recognize the characters or what they are doing, but the reader knows exactly what's going on (or they may only later put together clues to understand what was happening). Many times, characters will act on information that the reader knows to be untrue because they've learned otherwise from another character's perspective. Everything everyone says is subject to scrutiny; a character can be described positively by one character and negatively by another, and it's up to the reader to determine how they feel. Very little is straightforward in this book, and pretty much everyone is multilayered and interesting.
GRRM is infamous, however, for showing no mercy in killing off characters, and let me tell you, a lot of people die in this book. Main characters, secondary characters, tertiary characters, quaternary characters, some stableboy who just appeared a page ago, and also five dozen horses. Characters aren't killed off for shock value; they die because that is what happens to them. Usually, there is an important effect on the plot or the characters. Thankfully, GRRM writes some amazing death scenes, the kind that have you gasping and crying and shouting profanities but also have you admiring the skillful way the scene is written.
And GRRM is a good writer, even though he can get carried away with descriptions of food and armor and sigils and whatnot. Because the story is told from different perspectives (third-person limited), the writing is more personal than that of a Tolkienesque omniscient narrator. It's compulsively readable, and it's sprinkled with wry humor.
I hesitate to say anything about the plot and characters because I knew so little going in that it was so fun to meet everyone and learn everything as I went along, even if it was a bit overwhelming. Suffice it to say that the story concerns two houses, both alike in dignity—wait, no, the Starks have way more dignity than the Lannisters. Anyway, there are Starks and Lannisters and they engage in a game of sorts, perhaps involving thrones. Yes, in fact, that is all I am going to say about the plot except for this: this book is deliciously plotted, with pieces being set up without your realizing that's what's happening until it's too late, and everyone's actions have consequences, often dire. This is basically the Wire of books.
A Game of Thrones is a hell of a book, the sort of book that, once you get into it, you want to do nothing else but keep reading. And if you'll excuse me, there are four more books in this series I have to read...