What is the theme of dear john by nicholas sparks?

If you know what a Dear John letter is you understand. If you don't here's what a Dear John letter is, here it is. A Dear John letter is one of those letters a you would write to someone that you might run away like Dear Mom and Dad, I've decided to run away. Something like that. I don't know why Nicholas Sparks made that his title because the book is about two people that basically live with each other through letters. Hope this helps a little bit.

there really is no meaning he just named it that because throughout the book the boy and his girlfriend Savannah writes letters to one another and his name happens to be john.