A Storm of Swords travels down some shocking narrative paths—even for this grisly, no-one-is-safe series—but what makes it so wonderful (easily the best of the ASOIAF books I've read so far) is how skillfully it maintains character growth and how farsighted it is in its plot upheavals. Even when characters don't get as much to do, Martin clarifies them like never before; Catelyn Stark, for instance, spent most of book two and the start of this installment getting on my nerves. Impetuous and internally guilting her son for not listening to her every word when he replaces his father as Lord of Winterfell, Catelyn does little in the aftermath of A Game of Thrones, and what does is typically stupid, ill-planned and ultimately disastrous. Yet Martin, without forcing the point, subtly casts Catelyn as a reflection of Cersei Lannister. Cersei is not a POV character, so she's typically been defined up to this point by people who hate her, which has only been slightly balanced by Jaime becoming a POV character this time. But having to put up with Catelyn consistently doing the wrong thing out of concern for her family helps clarify some of Cersei's behavior, especially as she finds herself in over her head back at King's Landing.
Martin continues to excel with his outcast characters: Arya Stark's struggle to escape various forces continues to toughen her, while the bastard Jon Snow faces temptations out in the wild that force him to decide who he really is. Sansa's growth from an infuriatingly naïve twit to a disgusted, all-too-world-weary young woman trapped by decorum and the violence underneath it have transformed the series' worst character into one of its most compelling. Sansa does the least of any character, but that is because she is powerless to move, and the rosy chivalry of her thoughts in A Game of Thrones has given way to unending terror and a hatred she can only just suppress. But, as ever, the star is Tyrion, who rose so very high in A Clash of Kings and now falls so very low because of it. His act of bravery at the climax of the previous book should have won him accolades and acceptance. Instead, it incapacitated him long enough for his considerable progress at King's Landing to be entirely reversed. It all goes to hell for Tyrion in this book, and by his final POV chapter I don't know whether to feel pity for what his resentful family has foisted upon him or scared to see what he'll do next.
Martin leaves space between his climax and his denouement, and never more so than here, where the grisliest, most stunning action occurs just past the halfway mark. But if the shocks more or less abate by the end of A Storm of Swords, the story certainly doesn't, and the sense of dread that hangs over this series has never been more pronounced. The last two books ended on dour notes, but typically a few characters still held out hope. A Storm of Swords ends in near-total despair, where even the one character who enjoys a small victory is still left to the enormity of his situation. A Game of Thrones and A Clash of Kings pushed Westeros nearer and nearer to the brink, but the wholesale slaughter of A Storm of Swords appears to have finally pushed this series over the edge. I am both eager and terrified to see where it lands.
