At the Earth's Core is a 1914 fantasy novel by 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.
The author relates how, traveling in the Sahara desert, he has encountered a remarkable vehicle and its pilot, David Innes, a man with a remarkable story to tell.
A Princess of Mars (1917) is a science fantasy novel by Edgar Rice Burroughs, the first of his Barsoom series. Full of swordplay and daring feats, the novel is considered a classic example of 20th century pulp fiction. It is also a seminal instance of the planetary romance, a sub-genre of science fantasy that became highly popular in the decades following its publication. Its early chapters also contain elements of the Western. The story is set on Mars, imagined as a dying planet with a harsh desert environment. This vision of Mars was based on the work of the astronomer Percival Lowell, whose ideas were widely popularized in the late 19th and early 20th centuries.More info →
Pellucidar is a fictional Hollow Earth milieu invented by Tarzan creator Edgar Rice Burroughs for a series of action adventure stories. In a notable crossover event between Burroughs' series, there is a Tarzan story in which the Ape Man travels into Pellucidar.
The stories initially involve the adventures of mining heir David Innes and his inventor friend Abner Perry after they use an "iron mole" to burrow 500 miles into the Earth's crust. Later protagonists include indigenous cave man Tanar and additional visitors from the surface world, notably Tarzan, Jason Gridley, and Frederich Wilhelm Eric von Mendeldorf und von Horst.