The first book, A Game of Thrones, established the world order. King Robert was the king and Ned and his lovely family lived happily at Winterfell and the seven kingdoms were at peace. Then Cersei and Jaime had to fuck everything up by arranging the death of Robert. Everyone was sufficiently suspicious and annoyed by this that they all had different ideas about who should be king. And so instead of working hard in the fields and storing extra food for the upcoming decade-long winter, they decided to burn all the fields and kill all the healthy young men in battles.
When we started out in A Clash of Kings, there were four kings: Joffrey of course; Robb who was declared King in the North; Stannis who probably should be the king, and Renly who seemed to come out of nowhere.
Stannis saw off Renly. The Lannisters saw off Stannis (at least for now; we're not quite sure what happened to him after the battle). Robb won some minor battles but I think he has some big battles still to come.
Meanwhile Sansa no longer has to give Joffrey heirs, but she might have to give him bastards. Arya had a great adventure escaping from King's Landing with Yoren and ending up as Bolton's maid. But Bolton's bastard has burned Winterfell and is presumably ravaging the north in general for some reason or other. Arya has escaped and is now heading for Riverrun.
Theon forsook the Starks and mainly managed to help Bolton's bastard and otherwise spread misery.
Jon went out on a great ranging and discovered quite a lot about what the wildlings are up to, such as that they were searching for something but are now heading south. He's going undercover to find out more. But I'm worried that he'll go so deep undercover that neither he nor anyone else will know if he is wildling or watchman.
Bran had a bit of a go at being lord of Winterfell but ended up on the run and will probably have an adventure a bit like Arya's, as will Osha and Rickon.
The other forces of Winterfell are around somewhere. I expect they will help Robb but I also expect it will be a long time before he gets home.
Catelyn tried to stop Renly and Stannis from fighting but has ended up largely forgotten at Riverrun. All that fending off Tywin Lannister was probably for nothing since they turned up unexpectedly at King's Landing instead. In fact I wonder if the whole Riverrun thing was just a feint.
Jaime Lannister spent the whole book in a dungeon. He was almost rescued by Tyrion; he might have been killed by Catelyn.
Tyrion pretty much ensured the battle at King's Landing was won, but I suspect he won't receive any thanks for it. Everyone is either annoyed about the fires, wants to kill him, or has failed to notice what he has done.
And Dany trekked across the desert, had some adventures, and his now heading back with her dragons and some Dothraki to Westeros, or wherever Ilyrio wants her to go.
This has been the traditionally depressing middle book of the trilogy and I am sure that in the third part, good will prevail over evil and everyone will live happily ever after.
Who will end up on the throne? Arya is sufficiently badass to become the first Queen of the Seven Kingdoms. Or it might be Dany. Bran has superpowers that would be very useful for a king, or possibly a hand. Or he might be Varys: The Next Generation. It can't be a Lannister, surely, or else why bother with all these novels? And it had better not be a Greyjoy or a Bolton. Personally I think the best possible king would be Hodor.
