ERB began work on a sequel to Tarzan of the Apes almost immediately following All-Story's purchase of the initial tale. It was written in two months - Dec. 1912 to Jan. 1913.
Various working titles for the book during its composition include "The Ape Man" and "Monsieur Tarzan".
The action picks up soon after Tarzan's self-renunciation in Wisconsin at the end of the first book.
In this adventure, we get to see the Ape Man in very foreign surroundings, with the first part of the book taking place in Paris. Great fun to imagine Tarzan smoking cigarettes and drinking absinthe! In the latter part of the book, we are introduced to the lost treasure city of Opar - a place that Tarzan will revisit in subsequent adventures.