This is the second book of the Song of Fire and Ice series written by Martin. You really can't just jump into these books without starting at the beginning, so I'll assume you've read the first book already.
Martin picks up where he left off after book one, and he takes off running. The book is basically in the same format as the first, with a few new voices added in. Basically there are several men and a few boys fighting to be king. Namely Robb Stark from Winterfell, the heir apparent Joffrey Baratheon, and two of Robert Baratheon's brothers. In addition, Theon Greyjoy, Eddard Stark's ward, decides to throw his name in the hat and fight for his father's honor.
In addition to the wars and battles in the south, Jon Snow has traveled north of the wall to find his missing uncle. Although his story doesn't intersect with the main plot line, I hear it will by book three. Honestly, I was a bit bored by Jon Snow's chapters.
Of course, we can't forget Dany, in the East. Her story was my favorite from book I, but it slowed down considerably in the second book. She is still trying to build an army and secure ships for her return.
Overall, I think I liked book I better than book II, but I enjoyed both. I think the biggest obstacle in reading these books is the sheer length. At 969 pages, A Clash of Kings took me awhile to read. And I can't help but think I could have read 3 or four other books in that time. So while I may eventually read all the books in the series (there are seven planned), I might have to take a break for awhile and catch up on some of my other books.
Kind of a luke-warm review, I know. But if you've read their first book, I have a feeling you've already decided for yourself if you're going to keep going or not.