Before you send your book proposal to a publisher (or even talk to a publisher), you should do a SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis. Gail Martin, author of The Thrifty Author's Guide to Launching Your Book, suggests the following. And, any publisher is going to do something similar after you have presented your idea to them. If you will answer all of the questions before the publisher asks them, you will have a much better chance of getting your book published!
"Do a SWOT Analysis for your book. Your SWOT analysis should make clear your Strengths, Weaknesses, Opportunities, and Threats. Your business plan should have a goal or action that addresses each SWOT aspect.
What are your book's STRENGTHS and features that differentiate it from other books on the same topic?
What are the WEAKNESSES of you or your book? (Examples could range from lacking a distributor for your book, to having less career success in your topic than competing authors.)
What OPPORTUNITIES currently exist in the marketplace for books such as yours? (For example, during an economic downturn, books on budgeting and saving money soar in popularity.)
What are the biggest THREATS you see to the book's success? (This could range from you suddenly getting too busy with family, health, or work issues to suitably promote the book, to having a crisis occur that makes your topic out of favor.)
Once you have thought through these items, your book business plan should get clearer."