Series
Ciclo di Pellucidar.
We don't know whether this one is finished.
Nobody has confirmed the status of this series yet. That's a gap in our data, not a verdict on the books.
1 book here · 1959
Publication order
This is publication order — nobody has confirmed a different reading order for this one yet.
4
Tarzan at the Earth's Core
1959 · Edgar Rice Burroughs