All right, I admit, this is not great literature, but it is a terrific Tarzan adventure. Scientists discover a super light super strong metal, and don't waste their time figuring out the ways it could completely transform society - that would be boring, I guess. Instead, they build a giant blimp and head out on a high risk adventure to explore the earth's core. And, being wise, they invite Tarzan along to help out. It's amazing - the earth turns out to be hollow with a mini sun suspended in the middle, and animals from all sorts of eras running around. Apparently gravity is reversed inside the earth's hollow skin, so there is no fear of falling to your death. There are the usual excellent battles, awkward love story, and embarrassingly racist attitudes (although Burroughs seems to have toned it down in this one).
It was the stegosaurus episode that clinched that 5th star. A vicious stegosaurus decides to attack and eat our hero, so he spreads his plates flat, leaps from the top of a cliff, and glides down in a deadly flight. Paleontologists may object on many counts, but it is my favorite dinosaur description ever. ( )

The crossover just didn't work for me. ( )

The author's literary style is well developed and he set up and interesting story line in which for the first time Tarzan is lost. An American name Jason Gridley is set on rescuing David Innes from a lost world that lies under ours. A world with its own sun that never sets and the author can play with his ideas of evolution with the introduction of the snake people. And as in other “Lost Worlds” we have read about Tarzan has to fight prehistoric animals that the author claims are the ancestors to the creatures of Tarzan's jungle up above. With what seems like an entire world bent on the destruction of this intruder, Tarzan must persevere if he is to be successful in his rescue. ( )

One must remember there were years between the books in this seven-book series, thus the poor rating and reading of the previous book disappears as ERB hits his stride with Tarzan and Pellucidar thrown together. Pellucidar triumphs over Tarzan in the story-telling, though, as we are inundated with several tribes of humans and some new beasts. Probably the most interesting are the Hibibs, the "snake people," who have taken another path on the evolutionary ladder. the Habib are cold-blooded, egg-laying scaly-skinned, chameleon color changing creatures in human form. The other interesting draw in this book is the Red Flower girl. She sounds like someone I'd like to meet,and so far in ERB's writings, I haven't come up with any female that has the devil in her such as Jana does. ( )

One of the more outlandish Tarzan adventures, postulating a hidden world beneath the Earth's crust, Pellucidar, where Tarzan sets off in a dirigible with Jason Gridley to rescue explorer David Innes. Pellucidar is lit by its own central sun and populated by gigantic primitive beasts. Fairly routine but exciting adventures; a refreshing moment is when Tarzan discovers he is lost in Pellucidar, with its eternal central sun and a horizon which stretches up in all directions. ( )