Writing a book is like putting on your most gorgeous outfit for an all-night party with all the people you like. Writing a book proposal is like being kidnapped, in your oldest underwear, to convince some grumpy space-aliens why Earth should be saved.
So why am I writing about this here in Slashdot? Aside from the obvious reason (avoiding work), I am inspired by Lingqi's Japan journal to write about stuff going on in my real life, assuming that fellow nerds will be interested. In fact, more of us probably plan to write books some day than will ever visit Japan, which is a good thing for Japan, because those islands would sink into the sea under the weight of the world's potential authors.
A typical trade-book proposal is between 15 and 70 pages long. Most of that is bits of your book in progress--that part is no problem. The annoying things, in no particular order, are your author biography, proposed word count, market analysis, and discussion of the competition.
The author biography is where the author explains (third-person pronouns preferred) that the already incredibly-famous author is taking a break from singing on MTV, making touchdowns on ESPN, and saving the world on CNN to write a book that millions of people are already dying to buy. This for me is the underwear-talking-to-aliens part.
The proposed word count is a technical problem, and therefore kind of fun. I went at the issue like a typical nerd--looking up techniques on the web. It turns out the editors don't really care about the number of words at all--what they want is to figure out the number of pages, estimating 250 words per page. Since my book has lots of pictures, plus about a thousand jokes, most of them with titles (each title, taking up a line, is estimated at about 13 words), I spent hours this weekend computing words and pages.
Then, after I was all finished, I realized all I really had to do was to take down a book from my shelf that looked the right size and shape for the book I wanted, count the pages of that book, and that was my page count, or (multiplied by 250), that was my word count. So if you've read this far in my journal entry, you can write your book proposal faster than I did.