[PK]

I've had a few people not immediately "key onto" the concept behind this book, until I asked them, "Have you ever had a game in which exploring caves and tunnels didn't lead to some really cool adventure?" Without exception, their eyes immediately lit up as they became enlightened.

Fact is, underground exploration can feature into every genre from fantasy (e.g., dungeon crawling) to historical (e.g., pirate caves) to modern (e.g., spelunking action heroes) to futuristic (e.g., asteroid tunnels)! I'd say this is one of the most universally useful supplements we've put out in a while.