The Hollow Earth is a steampunk SF novel. In 1836, our young narrator Mason Reynolds leaves his farm, befriends the dissolute Edgar Allan Poe, and falls through a deep hole in the ice of Antarctica. Astounding adventures in the Hollow Earth ensue. Mason and Poe make their way back to surface. And then they encounter Poe's double...
Return to the Hollow Earth is Rucker's sequel to The Hollow Earth. Our young hero Mason and his wife Seela embark on a return voyage to the Hollow Earth with Edgar Allan Poe, traversing a great maelstrom at the North Pole. And when they return to the surface, they're in Santa Cruz, California--in the year 2018.