Size matters. Your book has to appear to be long enough to be worth the money you are charging.
Today, many of the high-speed web presses print signatures of 48 pages. As the paper goes through the press, 24 pages are printed on the top side and 24 on the underside. The most economical page-counts are in even signatures. One signature (48 pages) or two (96 pages) will not command the price you want for your book. A good minimum page count is three signatures or 144 pages. Additionally, since paper it the most expensive component of a book, 288 pages is a good upper limit.
If you need to lengthen your book, add resources to the Appendix: List other relevant books, videos, courses, mailing lists, associations, suppliers, etc. Now your useful text becomes a valuable reference. You do not want to pad the book with extra writing and dilute your message. Adding resources is a better alternative.
Other ways to lengthen the book–while making it more valuable and more interesting–is to add quotations, stories and illustrations to the pages and/or summaries at the end of each chapter. Be sure to lay out the pages with plenty of white space.
Leigh Cohn took three of his wife’s 30-page pamphlets on bulimia and combined them into a single book. They added resources, a two-week program to stop binging and a guide for support groups. Lindsey Hall’s 160-page Bulimia:A Guide to Recovery has been through five revised editions for more than 100,000 copies in print.
Since then, they have written nine books, established their own publishing company with more than 20 titles currently in print, launched an eating disorder resource catalog, and published a clinical newsletter at http://www.gurze.com/
A book full of resource material is not just a quick read, it is a valuable reference.
Dan Poynter, the Voice of Self-Publishing, has written more than 100 books since 1969 including Writing Nonfiction and The Self-Publishing Manual. Dan is a past vice-president of the Publishers Marketing Association. For more help on book publishing and promoting, see http://ParaPub.com/
Learn more about self-publishing from Dan Poynter.