Writing your book proposal

I'm frequently asked how one goes about getting their non-fiction book published. While there are pros and cons to traditional publishing, going the traditional route gives you (potential) access to a distribution network that self-publishing can't.
Simply put, this means that your book, if it's good and it's published by a global house, will likely appear in countless book stores and possibly translated for publication across the globe. 

Of course, there's a catch. Unless you're already a household name, publishers won't accept a book idea, but they generally won't accept a manuscript either. What do they want? A professionally written book proposal that's structured a certain way and contains the content they're looking for. If you want your book to be accepted for publication., you must write a book proposal. The proposal I co-authored with Drew Williams was a hundred pages long! You may not need to go to that extreme, but the work must be put in because publishers need to see how they can make money from your book.Here's an insider's description of how the process works, from the publisher's point of view. Not that your book is called a "project", because there is much work to be done to it, and with it, in order to safeguard the publisher's reputation (and of course help their bottom line). 
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The project
Projects usually arrive on an editor's desk in one of two forms: most commonly a synopsis, but sometimes a manuscript. The latter is fairly rare. Most authors would prefer to write and present a synopsis and find out whether the publisher is going to be interested or not. They would prefer not to have to go to the trouble of writing a whole book, only to have it rejected. A synopsis should consist of the following:
• A rationale for the book—which is the author's assessment of the need for (or demand for, or attraction of) the book. Here the author is justifying why this particular work should be published.
• A detailed description, chapter by chapter, of the book.
• The author's assessment of the market for this book—who will read it, and why.
• Contextual information, such as examples of what are often called "competitive texts"—what is wrong with them and why this proposed project will be superior. Similar information can be presented showing that this particular genre of book is enjoying success with the reading public. In sum, the author is using his or her powers of persuasion, harnessed with information gleaned about who is buying what books, and why, to convince the editor that there is a demand for this type of book.
• The author's assessment of how long the book will be and how much time he or she needs to write it.
This is usually enough information for editors to start working on a series of procedures that might lead them to the point where they can recommend to their colleagues that publishing this book is an acceptable commercial risk. Remember, when recommending a book to your colleagues, you are asking the company to invest in it. Investment means money and a lot of effort, so editors must get this recommendation right.
Occasionally, you will find yourself dealing with an author who does not want to put the effort into writing up a proper synopsis. The solution here is a simple one: turn them down. Writing a synopsis is the most effective way for authors to think through properly what they want to write. An idea is not enough: execution is everything. So, if they are not prepared to put themselves through the disciplined process of working out how their ideas can turn into a viable, structured text, then they are probably not up to writing a book or handling the publication process.
[Excerpted from Gill Davies and Richard Balkwill's The Professionals' Guide to Publishing: A Practical Introduction to Working in the Publishing Industry (Kogan Page)]
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Of course, if you use a ghost writer to write your proposal, you will dramatically lower the risk. Here's what Michael Larsen has to say in his widely read book, "How to Write a Book Proposal" (Writer's Digest Books, 4th Edition). It's my bible for writing proposals:

"How to Write a Book Proposal" by Michael Larsen

The bottom line: your proposal is as important as the finished book.