Credit goes to /u/ReadythePies for posting this in r/asoiaf. When George R.R. Martin wrote A Feast for Crows and A Dance with Dragons it was one manuscript. Instead of splitting it into parts one and two he decided to split by point-of-view characters in certain locations on the suggestion of author Daniel Abraham. A Feast for Crows had all the characters South of Westeros and the Iron Island and A Dance with Dragons contained all the characters from the North and in the general Meereen area.
This link however suggests how you can read them together to form one cohesive novel as originally intended. I think when I eventually reread those two books this is how I will do it.