So a proposal for a new book has to do two main things: first identify a market niche that your idea will sell, and second, convince the publisher that you can write. You do that with an outline and a sample chapter. Those are the core bits of a proposal. There are other things, and most publishers have web sites like Addison Wesley's Write for us or Writing For O'Reilly. Think of each of these as a reason for some mean editor who doesn't understand you to disqualify your book, and make sure you don't give them that reason.
Adam didn't do too badly, his book was reviewed on the front page of Slashdot.
I wanted to write a book about how the voting machines industry blew their public relations, but never put together a proper proposal, so I have a lot of respect for writers with the discipline to do this.