The how-to book was written by Justin Gohde and Marius Kintel, OpenSCAD's primary author and maintainer, and can be had for $18 in the No Starch Press "Coding for the Curious" Bundle.

That's $6 off its regular ebook price, and comes with 10 other programming books from the publisher that can help you learn C++, Ruby, CSS3, and more. Even more if you opt for the 18-book $23 bundle, which adds instructional texts for JavaScript, PHP, R, and more, still for $1 less than the OpenSCAD ebook's usual retail price.