CentOS - Jul 2012 - Is gnome-devel-docs supposed to work with devhelp?

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?

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