Google Groups (which hosts our mailing list) will no longer support serving files past November 1st, so we've set up a new site to hold copies of the book as we work on it:
http://exploring.liftweb.net/
The Google Group will remain the primary means of discussing the book, and the new site has links to the issue tracking and source repos, which also remain the same. In addition to the PDF version of the book, the new site will also host an online HTML version of the book, as well as a downloadable HTML archive. Feedback on the book and/or site are always welcome!
Thanks,
Derek