The PDF is available for immediate download. It has an ugly styling, hasn't been checked much, and probably has a bunch of other problems, but it's there.
For those interested in the mechanics behind this: the book is written in an XML format called DITA. This site stores the book as DITA as well. I just added a feature to export the book contents into a ZIP file, which allows me to use existing DITA solutions for PDF creation.
Next step: write some nice Haskell-based DITA tools and try to get some automatic PDF generation in place.