I believe they based the movie off of this...or one of the several dozen movies released in the past few years dealing with an intrepid group of explorers getting stuck underground with subhuman cannibal mutants anyway.
OK, twist ending aside, the movie wasn't so terrible - all it lacked was the grand scope. This is not one little tribe of cannibal monsters we're dealing with: all over the globe the simultaneous discovery is made that deep, deep underground the earth is not so hot and supports and entire global-spanning species that has forever been preying on us and inspiring out deepest fears of Hell.
This is a great summer read to get sucked into, it's thick but the pace is swift and the revelations always entertaining. I dock the book points only because it's been awhile since I've read it and I keep thinking about how absurd the whole hollow earth thing is.