A novel in two parts

Simply it is about two personas who have their own stories but, actually it is the same stories seen though two eyes. It explores the spirit of a person, what if two spirits shared one body, this will ne two stories in one book. and at the end the two figure out what really is, and it is something that can hardly be comprehended it seems so "out there" impossible. All along the two created explanations for things that could be understood no other way.