This is where you download the full eBook (376 pages) as a PDF and an ePub file. Not sure? Read the free preview (3 chapters) or check out the free audiobook first. If you like that, go for it.
This is version 1.9 of the book. It was updated in December of 2016.
What happened between version 1.0 and this one? Nothing, just fixed some typos and improved the layout somewhat. Versions below 1.8 may appear to contain fewer pages, but that is only because I increased the spacing between the lines to improve readability of the PDF.