I've borrowed the idea, and have started a small-scale test of the script on Wikibooks. Naturally, i've changed a few details, and discussed some uses with other Wikibookians:
- CSS pages are loaded in per-book, not per-page. This way book authors and editors can make large changes to the appearance of a particular book by making edits to a single file (and without having to rely on volumes of specialized formatting templates).
- Per-book CSS files might be located in the main namespace, in the book itself. These pages wont be protected by default which means that vandals will be able to mess with them, but regular authors and editors will be able to play with them more as well. This is an idea that some other users have suggested, and is worth testing.