The First Pellucidar Collection

The First Pellucidar Collection includes two full-length novels about the fictional Hollow Earth Pellucidar.
At the Earth's Core is a 1914 fantasy novel by American writer Edgar Rice Burroughs, the first in his series about the fictional Hollow Earth land of Pellucidar. It first appeared as a four-part serial in All-Story Weekly from April 4-25, 1914. It was first published in book form in hardcover by A.C. McClurg in July, 1922.
Pellucidar is a 1915 fantasy novel by American writer Edgar Rice Burroughs, the second in his series about the fictional Hollow Earth land of Pellucidar. It first appeared as a five-part serial in All-Story Weekly from May 1 to 29, 1915. It was first published in book form in hardcover by A.C. McClurg in September, 1923. A map by Burroughs of the Empire of Pellucidar accompanied both the magazine and book versions.