I'm at the Wikiconference NYC today and just got out of a very interesting keynote speech, and Q+A session lead by Jimmy Wales. As can be expected in a room full of Wikipedians, lead by the man who founded Wikipedia there wasn't a whole lot of talk about the various sister projects such as Wikibooks. However, mention of Wikibooks was raised at one point during a question about textbooks and instruction.
Jimmy Wales stabbed on a point that I've known for a while but haven't really vocalized before. The problem with Wikibooks, he says, is an issue of K-12 adoption. To be adopted in a classroom a book must comply to a pre-set standard curricula. Without curriculum compliance, there is no hope whatsoever that the book will ever be used in an actual classroom. Without a target audience, it's hard for editors to be motivated to write books, and the cycle continues. This problem is compounded by the fact that many existing curricula are copyrighted and not available to us for free use.
Wikibooks has done pretty well so far in the area of college-level textbooks. Many of our editors are college students or college professors (or graduates who managed to retain some of their knowledge), and there has already been good feedback from college courses that are using our books as part of their programs. So, there's a feedback loop here that reinforces and encourages more development in these books. Our collection of college-level books therefore is of a much higher quality then our collection of K-12 books.
People have said in the past before that Wikibooks has a dearth of quality books for young children. People have also mentioned in the past that books on Wikibooks don't follow standard curricula. It's the interplay between these two items that is something I've never quite put my finger on before, but that Jimmy nailed. This doesn't necessarily explain why Wikijunior is so stagnant (since children younger than school age don't need to follow a curriculum), although Part of Wikijunior's target demographic does include school-aged children as well.
Luckily, I don't think that this problem is a hopeless one. I think that in time we will cross the hurdle and break the feedback cycle of stagnation. A big part of this is the license migration, so now Wikibooks is more compatible with CC-BY-SA content (which is how most other open-content textbooks are licensed). I also think that there are efforts that can be made to conform to existing (although admittedly not often used) free standard curriculums, and also to put pressure on governments to make more existing curriculums freely available.
I would love to hear more ideas on this topic, to try and start brainstorming ways we can improve our K-12 books.