I just started it (about 100 pages in) so I don't have much to go on yet. I wish I hadn't gotten so involved in a series that isn't complete yet. I hate waiting for the next book!
As always there are a number of different threads but the great bulk of the time is spent with Jaime and Cersei Lannister. Cersei is in full Lucretia Borgia mode...now that she has obtained power. At times she is as wily as Elizabeth I, at others she appears to completely absorbed in self-destruction. Martin does a great job with her. There are many characters who won't appear at all till the next book.