The sixth series in the Pellucidar series finds David returning from his expedition to find Von Horst. He is captured by the women of Oog. Oog is a land were the roles of women and men are reversed. He manages to escape but then fall into captivity by the Jukans.
It is here that David is reunited with his mate Dian. She had set out to find David and was also captured by the Jukans. They both escape and have further adventures with giant men, giant ants and floating islands before reaching their home of Sari.
The final Pellucidar novel that was published in Burroughs lifetime. The story was a solid adventure if not distinguishing itself in any special way. I would place this in the good not great category.