My friend handed me a book of nonfiction her uncle had written and asked me for my opinion. I scanned through the first few pages and handed it back. “He doesn’t say what the book is about. I have no way to evaluate the book without knowing what his point is.”
The author of this book made a mistake that many young writers make, namely, not stating explicitly what their thesis is. Without knowing the thesis, readers can’t judge whether a book does what it says it will do because it never says what it will do. It’s like giving a person a car but not giving any directions. Where should the car go? Should the car pick up passengers? What is the purpose of the trip?
If you are writing a nonfiction book, essay, chapter or news story, you should alert the reader to your purpose. You can do that several ways.
One way is to write a headline or title which encompasses the main idea. “Twenty dead in tornado” and “Biden wins Pennsylvania’s electoral college votes” clearly state the main details of the article to follow.
Another way is to state in the first paragraph (or rarely, in the last, if you are leading up to your main point) the thesis of your writing. A classic example is the following: “Oppressed people deal with their oppression in three characteristic ways.” –The first sentence from “The Ways of Meeting Oppression” by Martin Luther King, Jr. The rest of his essay identifies those three ways and explains why one is best.
If you are writing a book, use your introduction to explain to your readers what the purpose of your book is and what they should learn. “You’re reading this book because you want your business to grow. I’m going to show you a proven system for making all this happen. –The Snowball System by Mo Bunnell
If your readers need to infer the main idea, they might stop reading. Too much work. So make sure you state early on what your point is.