Your introduction should be no more than one page long so that a busy person can scan read and still get a good idea of the overall message.
What are the main benefits that a reader will receive from this book? How will the knowledge in this book help them to improve? Summarise these in a simple bullet list:
- How to improve on something they are already doing?
- How to learn a new technique that will save them time or money?
- Give them greater insight into a specific subject?
Finish the introduction with a personal message to the reader. Speaking directly to your audience helps to show that the book was tailored for their individual needs.