Just finished my rereading of Jeff Long's Deeper. Its the sequel to The Descent(novel unrelated to the movie). Deeper was not as good as The Descent, but till a great read. If you haven't read The Descent you must. Long describes the caves/tunnels/underwater seas/etc. amazingly. The creepiness is there. The mystery is there too. Exploration of the deep subterranean, of an unknown humanoid species. This is not the mole people. Its vicious, harsh, wonder.
4/5 stars.