Trajectory presents classics of world literature with 21st century features! Our original-text editions include the following visual enhancements to foster a deeper understanding of the work: Word Clouds at the start of each chapter highlight important words. Word, sentence, paragraph counts, and reading time help readers and teachers determine chapter complexity. Co-occurrence graphs depict character-to-character interactions as well character to place interactions. Sentiment indexes identify positive and negative trends in mood within each chapter. Frequency graphs help display the impact this book has had on popular culture since its original date of publication. Use Trajectory analytics to deepen comprehension, to provide a focus for discussions and writing assignments, and to engage new readers with some of the greatest stories ever told. "Pellucidar" by Edgar Rice Burroughs is the sequel to the science fiction novel, At the Earth's Core. In this story, David Innes returns to the Inner World of Pellucidar in an attempt to rescue Diane. He undertakes an expedition thousands of miles across the inner earth in an effort to save Diane.