Last weekend I finally picked up a copy of Zak Smith's Vornheim at Dundracon.
I'd been meaning to pick it up for a while, but when it comes to reference material - particularly in the rarified world of RPGs - I have learned to be very circumspect. Who does not remember picking up their first copy of the World of Greyhawk setting? The maps, the charts, the tables, the NPCs, the names, the places, the histories, the racial politics, the inclement and average weather tables, the holiday calendars... yawn. The indefatigable minutiae!
In general I try to avoid anything of that type; where rules are written into a setting in such a way that an alleged "game aid" becomes an enormous albatross around your neck, tying you to a particular setting and condemning you to struggle against a plethora of stat blocks, charts and oblique references to canonical material FOREVER. Or at least until you chuck the manual and write up your own homebrew.