Just a short update this morning (I know I've been slacking!). The Wiki-To-Print extension has been installed on all language Wikibooks projects. I've been waiting for something like this for years now, so I'm very happy to have it. Of course, it goes live the day before I leave for vacation, and I can't play with it for a whole week!
There are a few known issues with this extension, so I would like to ask people to come check it out and give some feedback for it.