How To Write a Book in 30 Days


8. Your Book’s Theme

Idea vs. Theme

Now that you’ve identified your perfect reader and you’ve determined the benefit you’re offering your reader, it’s time to nail down the main idea and theme of your book. 

“You can’t tell any kind of a story without having some kind of a theme, something to say between the lines.”
Robert Wise

American film director, producer, and editor.

Although ‘idea’ and ‘theme’ sound like much the same thing, they have some subtle and important differences that will help you keep your book on track for the reader.

Module 8: Your Book's Theme

by Steve Spillman | How to Write a Book in 30 Days


First, let’s discuss the main idea of your book. The main idea is what your book is about — the general content of your story. In my example, How to Write a Book in 30 Days, the main idea of the book is: “The process, the time-tested tips and practices of writing a successful nonfiction book in just 30 days.” That’s what the book is about — that’s the nuts and bolts anyone can follow in an organized, sequential way; sort of like (I hate to admit) a cookbook or instruction manual. But the main idea of the book is just the surface, the ‘as advertised’ guarantee of the book. Do you want to write a book in 30 days? How to Write a Book in 30 Days can show you how

But is a cookbook or instruction manual really what the reader is asking for? Shouldn’t there be a little something more under the surface?


Shouldn’t there be a ‘more-than-advertised’ benefit to the book? That’s where your theme comes in. Your book’s theme should be felt in the reader’s gut, not in her head. The theme is the real reason your reader is buying your book. What’s the theme, then, of How to Write a Book in 30 Days? Here’s my theme: “The process of writing a book is definable, finite, and, most of all, achievable for any writer, regardless of previous experience — that means you! You can write a book, your book, in just 30 days.”

Do you see how the differences between ‘idea’ and ‘theme’ can be subtle but so very important?

The book Big Mountain, Bigger God tells the story of the Mullett family’s sixteen-year battle with two of their children’s congenital heart defects. The story, the insurmountable trials and pain they suffered, is the ‘idea’ of the book. But the Mulletts learned a profound lesson in the midst of this ‘no-win’ battle – that God’s ways are far greater than man’s circumstance and that God’s grace, mercy, and strength are sufficient, even when we don’t understand the why of innocent suffering. That is the ‘theme’ of Big Mountain Bigger God. The theme is what comes to reside in the reader’s heart.

Idea vs. Theme

Take a moment to ask yourself:

“What is my main idea? What is this book about?”

Then ask, “What is my theme? What truth do I want to plant in my reader’s heart?

If it’s easier, think of it this way – your idea is the carrier, and your theme is the thing you’re carrying. Your idea is the treasure chest; your theme is the treasure inside.

Now get to work!


  1. What is your book’s main idea? What is your book supposed to teach or share with your reader? Take a sheet of paper, an index card, or a Sticky note and write “IDEA” on the top, then write your anwer below.
  2. What is your book’s theme? What is the lesson you want your reader to come away with from reading your book? What truth or treasure do you want to plant in their hearts? Take a sheet of paper, an index card, or a Sticky note and write “THEME” on the top, then write your anwer below.
  3. Post your “IDEA” and “THEME” paper/note card/Sticky where you will see it every time you sit down to write. Read it to yourself before each writing session. Live by it when you write. It is your guide.

Next: Module 9: Do Your Research

Click here to visit module 9 “Do Your Research”