Yea, its not quite done yet. Getting there...
I think having to stick with an update schedule helped U_K stay focused, (Probably to the point of burnout) But I can't speak for the man.
It certainly was cool seeing some of the elements of the book evolve over time. I think U_K misjudged how much writing this book would take initially. (
IIRC, it was about this time LAST YEAR that U_K thought he would finish... But things come up, and no one I know can just sit down and churn stuff out 24/7)
It should be done 'soon'. This recent doldrum of nothingness aside, if U_K works at his most efficient rate, I can realistically say December as my guesstimate. (By December, I mean done and errata'ed and off to the presses) Perhaps U_K has secretly already finished and is mocking us right now. Perhaps it comes out tomorrow. This is U_K. Who can really say?
(And U_K, I know you are doing the work as fast as possible while trying to remain sane. It's almost over... After this, only like 10 more books and...

)