I've taken a little bit of a break from book categorization myself, other things in life have been eating up a lot of my time. However, just because I've taken a break and have stopped blogging about it doesn't mean that categorization has stopped en masse. [[User:Adrignola]] specifically has been doing a lot of work getting our terrible category system cleaned up.
The Category: namespace at Wikibooks has been, to put it nicely, a trash heap. There are a lot of reasons for this, stemming pretty far back in the history of the project. A lack of a clear categorization policy resulted in a number of ad hoc categorization methods being implemented by various people. Early in the project we also had a series of "bookshelves" pages where books were organized into lists by subject manually. Certainly seems like a waste of effort now, but the bookshelves served us pretty well for a pretty long time.
A while back we decided to get rid of the bookshelves and replace them with a Category-based alternative. However, instead of using plain category pages, we decided to go with Dynamic Page Lists on our new Subject pages instead. So even though we are moving in a better direction, we still have plenty of excuse to keep sweeping problems in the Category: namespace under the rug. All that matters to us now is how well things appear on the subject pages.
That's not to say that organization of our category pages is unimportant, in fact it's very important since categories form the underbelly of our whole organizational structure. If they're messy, nothing above them will ever be as good as we need it to be.
So, I think it's very cool that people are working to make the category pages better, and I sincerely hope that the good work continues.