If you are uninitiated into proposal writing, let me warn you that it feels like creating a graduate-level research project or a complex business plan. I spent as many months composing my proposal as I did my sample chapters. A first time book author needs a book proposal whether you plan to search for an agent or sell directly to a small press.
Some authors like to finish their entire book before writing the proposal, but I chose to write my proposal after I finished three chapters of my manuscript. I like the idea of being able to send off my proposal, so it does the work of selling my manuscript, while I leisurely finish the fun part of writing—my actual book. Of course, if the proposal does its job and I sell quickly, that’s even better. I do work more efficiently when I am under a deadline.
The proposal can also help authors focus their project. By the time you finish your proposal, you will know who your audience is, how big your potential readership is, and how the book should be marketed to them. You will know where your book fits in the literary conversation about your subject: who else has written on the same topic and how your book adds to what is already published. As part of the proposal, you will also develop an outline or expanded Table of Contents.
There are many books on how to write a book proposal. Here are the two main resources I used to create my proposal:
Website How to Write a Book Proposal at Adler and Robin Books. http://www.adlerrobin.com/howto.html
When you are serious about finding an agent and selling your manuscript, settle down and study how to create your proposal. Then attack it like a Master’s thesis. Good luck!