I've undertaken a personal mission to fix the categorization system at Wikibooks. Last week I went through and recategorized all the Fine Arts books. Today, I've just finished going through the list of Humanities books. I had to create a number of new subject pages to hold the various books, although there are probably more that I could have created. I tried to weigh our need for precision against the number of books we had in various categories. The more books we had on a given subject, the more deeply I would subcategorize things.
Anybody who knows a thing or two about the Fine Arts or the Humanities subjects should go through and double-check my work. Also, anybody who is more aesthetically-minded then me could go through and make these pages look more pretty. If somebody wants to join in my organization crusade, I would love the help!
I don't know what subject area I will tackle next. I was thinking about doing Social Sciences, but I might also like to look at Mathematics. I was also thinking about moving the various Medicine and health related books out of the "Science/Life Science" subcategory into a top-level "Health and Wellness" category. I'd like feedback on that idea too.