Hard-coding of "Next" and "Previous" navigation links is a bad idea, BTW. What happens if you want to reorganize your book or add a new module in-between two existing ones? It is better, IMO, to just have a link to the book's contents page and start page. The "Next"/"Previous" functionality should be done by the software, but that hasn't been coded yet (our developers have other, far more important things to work on right now).

See http://meta.wikipedia.org/wiki/MediaWiki_User%27s_Guide for an example of how I think Wikibooks should be implemented until we get the WikiBook functionality into MediaWiki. Numbered modules are also a bad idea for similar reasons.

-- Daniel Mayer (aka mav)