It'll be interesting to see how many copies of this are sold, seeing as we are giving the content away for free electronically. Personally I find it much more convenient to have a book than to print out a PDF. And I should point out that we welcome further contributions to the documentation, so if you want to see your name up there in lights...I mean...on the front of a book, start sending in your chapters now!
Technical notes: The LaTeX for the PDF was generated from reStructuredText using a development version of Sphinx 1.1 so that URLs would be included as footnotes. The source is stored in a Mercurial repository at BitBucket. Feel free to fork to fix typos!
Image credit: Tim O'Sullivan