Since we are on the topic of math textbooks, I will suggest the No bullshit guide to math and physics which is a math textbook written specifically for adult learners. See http://minireference.com/ for more info.
<discl>I'm the author</discl>
<discl>I'm the author</discl>
I agree that you don't need to read thousands of pages to learn calculus. However, I don't want to stop at calculus. Basically, what I'd really love to have is a "mother of all maths textbook" -- a thick and heavy tome that compacts information from all the other thick and expensive books (which I'm never going to read) and different fields of mathematics. With enough detail that you can actually learn from it -- so it shouldn't be just for review and looking up formulas you couldn't memorize. I'd like to call it a reference book I can forever keep in my bookshelf (under my bed) and always look in it if I'm unsure about something...
If someone has book suggestions, I'm all eyes.
For a more "math for general culture" I'd recommend this one: http://www.amazon.ca/Mathematics-1001-Absolutely-Everything-... which covers a lot of fundamental topics in an intuitive manner.
I have both books on the shelf, but not finished reading through all of them so I can't give my full endorsement, but from what I've seen so far, they're good stuff.
http://en.wikipedia.org/wiki/%C3%89l%C3%A9ments_de_math%C3%A...
Do you plan to release an ePub or mobi-format book? I'd prefer to read it on my ereader, and PDFs don't reflow on smaller screens.
Do you know of any math books that are available as .epub? I'd like to see how they implement equations... PM me if you would like to be a beta tester.