Dan,
Good of you to take on such a job. I'd like to do my part. I can't offer much, but I have some free advice. (The only guarantee, you will get your money's worth.)
Rather than relying on people reading this thread in a rather obscure area of the board (I rarely pop in here), why not review the board and see what questions are most frequently asked, review the level of the enquirer (newbie, adept, pro, guru) and start by answering those questions first. Not only will this provide the most bang for the buck when buying your book, as there are a lot of repetitive questions, but the board here also provides many ready made solutions to those questions if the user had only searched.
Structure your book to take the user from absolute n00b to at least adept. Gather relevant links and information from other sources in geometry, physics, algebra, etc. You don't necessarily need to duplicate it in your book, use the web links so that original authors will get due credit. (Permission may be required.)
If you are going to focus on scripting, then assume that the user knows ZERO about modelling and animating. When you must touch on these areas, do so fully, again with links and other sources. I don't know how many users have asked (me amongst them!) why "tutorial-de-jeur" didn't work, when we were using the guard model instead of the wizard model, which lacks a certain set of animations (swimming).
Lastly, if you charge for your book, keep it affordable. Yes, you are putting a lot of effort into this. Yes, it will take a long, long time. Yes, if you charge an extra buck, you'll make that million faster. However, your potential audience increases as your price drops.
Good luck,
Mark
