The book begins with four claimants to the throne of Westeros; it finishes with the same amount. All the major political figures of the first two books start and end in the same place with only one major incident at the book's climax, but without much actually being accomplished. A major inclusion is House Greyjoy, whose power was hinted at in the previous book, A Game of Thrones, but even they - point-of-view character Theon aside - are firmly sidelined.
A case in point: one of the would-be Kings dies. It's intimated how, but never described. On one page is a parlay, the next sees one of the delegates back home with scant reason. The claimant is dismissed quickly and without the care taken in describing his encampment, feasting tendencies or plans for a new Kingsguard. Martin obvioulsy felt he needed to spend those words elsewhere. Given the book's length, it was a a merciful - if odd - decision.
Unfortunately, this also means that the reader feels as if they are marking time until getting back to a storyline in which the plot actually advances. It makes for a disjointed read that isn't nearly as gripping as the first installment.
In many ways, the remarkable world Martin has created - like Tolkien before him - is his greatest achievement and a rod for his own back. While we learn more of the Seven Kingdoms, this is not matched by the activities of the major protagonists. Each POV character seems to have one task to accomplish - to meet parlay, to journey to the Outlands, to prepare for battle or to escape. Once this task is performed, they slide into obscurity.
War is made up of myriad finite, intricate moments which combine to form a much larger picture. This makes for some interesting times and some ... quieter ones. A Clash of Kings is certainly the latter.