Good project management says that planning before you start a writing project is a good thing. And many writing systems say you need to plan your writing before you do it. But people seldom come out and tell you straight up why.So here are five reasons you should plan while writing a non fiction book:1. Provide focus for your book. If you start off just writing a non fiction book you could end up with just about anything. Your book could go off into a side discussion. You could end up repeating information three or four times from different viewpoints. You could end up with a whole different book than what you started from. While a fiction writer can live with this (but shouldn’t) since the story lives only in the writer’s head, a non fiction writer can’t. After all, a non fiction writer’s subject is well known by many people. And they will know where the book should go. Even if the writer didn’t.2. Narrow down the options. There are a lot of options when writing a non fiction book. Even just in the physical form of the book. You need to limit those options or the tasks of designing and writing a book will become overwhelming. Besides, if you don’t plan you may find out that your book is outside the parameters your chosen distribution method can accept. Finding out your wonderful tome is too long for a publisher is not a good thing!3. Ensure there is a market for your book. A book without a reader is a lonely, pitiful object without purpose or value. By determining your market before you begin, and then writing to meet that market’s needs, you will ensure that more than just your mother will read your book.4. Keep your readers coming back for more. Getting an agent, editor and publisher interested is a good thing. But keeping a reader reading until the end is even better. That’s what will ensure your agent, editor and publisher talk to you again. The only way to keep a reader interested to the end with a non fiction book is to write what interests the reader from the start. You have to solve their problems or help them avoid a pain point. That’s the only way to guarantee your reader’s interest.5. Identify alternatives to this book. Look, you’ve done all the research. You’ve spent a lot of time, effort and maybe money up to this point. You’ve identified your perfect reader. Maybe you’ve even written your book. And sold it. Wouldn’t it make sense to get as much out of this expense as you can? By planning up front, you’ll be able to identify where you can write a second book. One that doesn’t rehash the same information. Or you can identify where you can present a course. One that will help sell copies of your book. By identifying alternatives to this book, both up front and as you go, you’ll be prepared when opportunities knocks.