Let's break this wild ride down. The book is actually three connected stories, which is part of its charm and its chaos.

The Story

The first part feels almost like a different novel. It's set in a future 1967 (which is hilarious to read now) where nations compete to reach the moon first. An American crew makes it, but their ship crashes. They discover the moon isn't a barren rock, but a hollow world with a breathable atmosphere and a dying sun at its core. The survivors find themselves in a savage land ruled by the bestial Va-gas and the more human-like U-gas. The main hero, Julian, is taken captive. The story then shifts to follow his life among these people, his rise as a warrior, and his love for a woman from a rival tribe. It becomes a planetary romance, full of chases, battles, and political intrigue, all under that weird interior sky.

Why You Should Read It

Look, this isn't deep philosophical sci-fi. It's pure, undiluted adventure pulp. Burroughs had an incredible talent for dreaming up bizarre worlds and then throwing his heroes into the deep end to see if they could swim. Julian is a classic Burroughs hero—brave, resourceful, and always landing on his feet. The world-building is the real star here. The idea of a livable interior moon, with its own ecosystems and ancient, fading civilizations, is just cool. It's the kind of concept that sticks with you. You're reading for the thrill of the next cliffhanger and the joy of exploring a truly strange place.

Final Verdict

This book is for the reader who loves classic adventure with a big side of imagination. It's perfect if you enjoy the swashbuckling feel of old movies or if you're a fan of authors like H.G. Wells or Jules Verne. Go in knowing it's from the 1920s—the pacing is breakneck, the science is fantasy, and some of the social ideas are very dated. But if you can view it as a thrilling artifact from the dawn of sci-fi adventure, you'll have a blast. It's a foundational piece of the genre that reminds us why we love getting lost in a good, escapist story.