There's also the cave-related https://secure.wikimedia.org/wikipedia/en/wiki/The_Descent_(novel) https://secure.wikimedia.org/wikipedia/en/wiki/The_Descent_(...

There's also the cave-related https://secure.wikimedia.org/wikipedia/en/wiki/The_Descent_(novel) https://secure.wikimedia.org/wikipedia/en/wiki/The_Descent_(... which I quite enjoyed.