O'Reilly Media and the authors of the current Learning Perl are looking foward to a book on Perl 6 when it's stable. Honestly, we started a long time ago, twice actually, and everything we wrote is now obsolete or has disappeared from the language. It's our hope that someday they'll settle on the final language, allowing us time to make the book.
When we start writing the book, we'll use this domain to let you participate in the process.
-- brian d foy, Febraury 2011