Most non-fiction books are sold on proposal, so you don’t need to have written the book already. Typically, a thirty page pitch should include:
- What the book is about and why it needs to be written and published now.
- Who you are and your qualifications for writing the book, emphasising your experience and suitability.
- Where your book would sit on the shelves, including similar or competing books that have already been published.
- A chapter of sample text, usually taken from an early part of your book, but not from its introduction.
- An outline of chapters, normally a page per chapter.
To do this you need a plan for each chapter and as stated you will need to provide text from a sample chapter. The next part is to show there is an audience. I can provide support in building an audience for an approach to a literary agent to sell your proposal to publishers. In fact, for non-fiction, it’s imperative to establish a market before you write your book.