Naturally enough, coverage is still intermittent. I do not know what sort of momentum it has picked up.
There is a skeleton - if little more - in place for Library and information science. (This is as part of the proposed Wikiversity, 'a wiki-based learning community'. One aspect of Wikiversity proposals sees the development of a range of learning materials, which would use, but also go beyond, the materials being developed in Wikibooks.)
From the Wikimedia home page:
Imagine a world in which every single person is given free access to the sum of all human knowledge. That's what we're doing. [Home - Wikimedia Foundation]YAGWALLM - yet another group with a library-like mission.