Define the theme of the book. Books about a particular subject like tactical folding knives usually focus on a specific aspect of the main topic to use as a theme. For example, the book may focus on the history behind the tactical folding knife. Another example may be the methods used to design and forge tactical folding knives. The book could concentrate on self-defense techniques with the knife. Choose a theme you are passionate about.
Conduct research in the area of your chosen theme. If your book is about how to make a tactical folding knife, then you could interview designers and manufacturers. Interview war veterans and law enforcement professionals to get information on the history or uses of various knife models. Compile and organize the information into a logical order to form chapters. For example, in a book about self defense techniques, begin with basic movements and progress to more difficult techniques in later chapters.
Insert photographs or illustrations. Visual aids add interesting content and may be instructive for the reader, depending on the theme. Forging techniques or self defense moves are easier to learn with visuals, for example. Find royalty-free images or create exclusive images for your book.
Create the text for your chapters based on the research you conducted. Add the photographs and illustrations wherever they are appropriate to complete the book.