One of the things the RPG industry is notorious for is bad or missing indexes. I've discovered over the last few years, some publishers don't know how to do them and some don't find them important. Others will drop them, supposedly, due to page count concerns. This last one I often find suspect, especially when there are ads or blank pages in the book (I have multiple publisher friends guilty of this sin).
One thing I can guess is they have to be pretty hard to do. Not necessarily the physical process of making one, so much as the decisions that go into what belongs in one. In most cases, it's not enough. You get your "lip service" indexes--the one-pagers. And sometimes you get behemoth indexes that never seem to have what you're looking for.
In the most recent episode of The Game's the Thing, I took part in a discussion about the index in Iron Dynasty, Way of the Ronin from Reality Blurs. I commented on how excellent the final of version of the book's index was. We had to cut the conversation, but I'd like to still give credit where credit is due. Apparently, the Blur's lead editor, Lyn Harm, is responsible for the index. It's six pages and includes a separate table index.
The size isn't what really hit me, it's the fact I have yet to stump the index when searching for something. According to Sean, Lyn actually kept a running list of what needed to be indexed as she edited the several versions of what became the final book. This process also apparently caught missing items, which needed to get added back in.
I am told the layout person is typically responsible for all matters reference in a RPG book--I have certainly never been asked to help in indexing when I edit--but I think the editor should certainly take part in the way Lyn did. Maybe this has been done before; maybe it's relatively common. I just know my experience, and it has never included anything involving the index.
Anyway... Well done, Lyn. And nice find, Sean.