The Hollow Earth

Simon & Schuster

The Kingdom of Agarttha: A Journey into the Hollow Earth

TarcherPerigee

Hollow Earth: A Coloring Book                    

CREATESPACE

Admiral Richard E. Byrd's Missing Diary: A Flight To The Land Beyond The North Pole Into The Hollow Earth

CreateSpace Independent Publishing Platform

The Hollow Earth: The Greatest Geographical Discovery in History

Da Capo Press

Hollow Earth: The Long and Curious History of Imagining Strange Lands, Fantastical Creatures, Advanced Civilizations, and Marvelous Machines Below the Earth's Surface

Claudio Ángel Nocelli

Return of the Giants from the Hollow Earth: Terra Infinita and the Inner World

Hollow Earth and Subterrestrials: Hidden Truths Beneath Our Feet: Journey to the most mysterious places on the planet to discover enigmatic peoples and ... beneath the Earth's crust (English Edition)

CREATESPACE

Messages from the Hollow Earth                  

Cross Cult

Hollow Earth 1: Dämonenfalle                    

Independently published

The Essential Hollow Earth Collection - Two Different Journeys Into Inner Earth: The Smoky God, Or A Voyage to the Inner World | The Iron Republic