Though now best remembered as the creator of the character Tarzan, Edgar Rice Burroughs was a prolific writer of science fiction and fantasy tales. This novel is the third entry in Burroughs' Caspak trilogy, following The Land That Time Forgot and The People That Time Forgot. Filled with more tantalizing details about the fantastical world the novels describe, this volume also delves into the science behind the story, positing a feasible evolutionary account for the survival of dinosaurs and other prehistoric flora and fauna on a remote island.