What is the main conflict in A Feast for Crows by George R.R. Martin?

A great war has left the Seven Kingdoms mostly in ruin and in a power vacuum. The last of a great line of kings has been killed and the succession is weak at best. Young King Tommen sits the Iron Throne now, but he is only a child. His mother rules as queen regent, but her lack of leadership skills and her own lust for personal power leaves her son's hold on the throne tenuous at best.