The Return to Pellucidar
The success of Thuvia gave evidence that the Mars stories could be spun out beyond the scope of the original trilogy, and in fact Edgar Rice Burroughs continued the series throughout his entire career. Although there were many more Tarzan books than Martian volumes, the first of the latter (A Princess of Mars) was the first Burroughs work ever published when it appeared in All-Story, while the last of Burroughs' books to appear in the author's lifetime was the tenth of the Mars series, Liana of Gathol. An eleventh Barsoomian volume, John Carter of Mars, appeared in 1964, although one of the two novelettes it contains is of dubious authenticity. (The book is discussed more fully in a later chapter.)
Even before Thuvia was published, however, Burroughs was back at his desk, his production quite prolific. Three projects attended to over the summer and early autumn of 1914 were sequels to The Cave Girl, The Eternal Lover, and The Mad King. The sequels were titled, respectively, The Cave Man, Sweetheart Primeval and Barney Custer of Beatrice. Because the two stories of each pair have appeared in combined editions ever since their first publication, they are generally regarded as complete novels rather than novelette pairs, and indeed the assignment of chapters and the general treatment of each book has been such as promote its being regarded as single novel.
The Cave Man has already been discussed along with The Cave Girl. The other stories involved present a curiously tangled sequence of fictional happenings as well as a remarkable interplay of characters. The actual sequence of writing—and of the events described in the stories—is (1) The Mad King, (2) The Eternal Lover, (3) Sweetheart Primeval, (4) Barney Custer of Beatrice. In other words, the two tales of Nu and Victoria take place between the two Luthan adventures; a number of the characters from the first half of The Mad King (as it appears in book versions) turn up in The Eternal Lover, meet