I just installed gnome-devel-docs with the objective of having a local copy of the gnome hig-book and now that I have it installed I don't know how to use it.

I had assumed that it would show up in devhelp but it doesn't. What I have is a bunch of XML files in /usr/share/gnome/help/hig-book/C, and when I try to view one with firefox it tells me "This XML file does not appear to have any style information associated with it. The document tree is shown below. "

What am I supposed to use to read the hig-book files?