Through the Fourth Book

In a faraway universe, there live some soulmates.

Two write books based on their lives. They are both best-selling authors.
The others are readers of these guy's books. There are four Novaks- Lucifer, Gabriel, Castiel, and Samandriel.
There are two Milligans- Michael and Adam.
There are two Winchesters- Sam and Dean.

What happens when they see each other with their favorite books?
What happens when their Letters are read?
What happens when these authors reveal themselves?

Well, we must delve into their story to find out.