N.L.
K.,
The movie that it comes from is called "Fireproof." I highly suggest that you watch it anyway. And in the movie, you will better see the name and author of the book it refers to. Also, it will be in the credits. I can't think of it right now. But I called a friend and if she calls me back with the name of the book, I'll write you again with it.
Very much worth it. Good luck, N.