Indiana Jones and the Interior World is the sixth novel in the series of original Indiana Jones stories published by Bantam Books, and the last written by author Rob MacGregor. It was released in December 1992.
Publisher's summary Edit
THE HIDDEN LAND BELOW
A strange mystery connects the whispering moai statues of Easter Island to the eerie ghost ship of Chiloé Island, leading Indiana Jones on a dangerous quest into a hidden interior world. Earlier Indy accidentally caused an imbalance between the two worlds when he disposed of a fabled but dangerous relic. Now, the leader of an unstoppable army uses this artifact to enter our world and for a deadly alliance with an even darker force....
For centuries man has told tales of a hollow earth, or an underworld, populated by a mysterious race and strange characters. Sometimes describing an underworld of death, sometimes another dimension, these stories tell of mermaids, ghost ships...and a cosmic balance that must be restored lest the powers within march to conquer the outside world—and only Indiana Jones holds the key!