In order to take the discussion about the proposed Tapestry 5 community book off the T5 user list, I've created a group on the topic . I've sent invitations to most (if not all) people who have expressed an interest in contributing, if you haven't received such an invitation, please visit the group (at http://groups.google.com/group/*tapestry5-book*<http://groups.google.com/group/tapestry5-book>) or send me an email and I'll send an invite.
Just as a reminder, the project is currently on Google code at http://code.google.com/p/tapestry5-book .