Just finished rereading...
At the Earth's Core
by Edgar Rice Burroughs
Probably my favorite Edgar Rice Burroughs story this book features some of Burroughs' finest world building and wastes no time getting right into the action. After a brief prologue where the narrator reveals that this story was told to him by a man he encountered while on safari in Africa, we are drilling into the Earth's crust with the main character David Innes and Perry the scientist responsible for inventing the spectacular machine. Thinking themselves about to die when the steering wheel becomes locked in place they instead emerge in a new world. One inside the Earth where a bright ball of gas in the sky creates a perpetual noon and prehistoric humans are enslaved by a race of evolved pterodactyl like reptiles. Their adventure is genuinely fun and exciting and the vivid world and creatures that Burroughs' creates are both a wondrous and terrifying. There's even an epic battle after David and Perry manage to unite the kingdoms of Pellucidar against the Mahars. The ending will likely have you wanting to read the other six novels in the Pellucidar saga. I would love to see this book adapted into another film.