This book is the start where you see a different side to Rhllor (Mellisandre's red god). He is also the god responsible for resurrecting Beric Dondarian and Catelyn. He/she seems to be the biggest reason Stannis goes to help the Night Watch.
It is interesting to note Barristan Selmy has gone to help Daenrys. He is old but held in high esteem and (still) seems to be a better knight than any of the current white cloaks. On this note, I'm warming to Jaime as a character - he is a lot more 'knightly' than his kingslayer tag.
Jon's assent to the Lord Commander's chair puts him in a powerful position, though you wonder how he will be able to stay out of the politics of the kings, especially with Stannis having provided him support.
Joffrey got what was coming to him. I (inwardly) cheered as he was choking
Margaery is lining up for her 3rd Baratheon husband - I'm not sure I'd want to marry her - she is just bad luck - watch out Tommen!
And on a side note - the clips and photos I've seen of the HBO series look bloody good!