As most of the relevant community already knows, there’s a O’Reilly Twisted book out. You can also buy it from an Amazon associate to help defray the twistedmatrix.com hosting costs.
An important question is being discussed as I write: what should the book’s code name be? If Programming Perl is the Camel book
it is argued, this should also be coded on its cover. So far, the orgy book
seems simplest, with the snake orgy book
as a backup if O’Reilly gets a bit wilder with their covers.