This answer is going to be somewhat unorthodox, but bear with me. First, I will only be discussing Jean-Louis Njemba Medu and Cameroon right now,, because there is no meaningful relationship or interconnecdmess between Cameroon and Nigeria or the authors in any way here, at least not in any form that is helpful:

Now, there was no literary scene in Cameroon. They may have been speaking French in the '20s, but there was no Bantu Gertrude Stein. There were no indigenous writers. There were almost no indigenous readers. You have to reframe the way you're thinking about this topic. As Marie-Rose Abomo-Maurin (whose work I will be relying on very heavily here:) puts it,, " there was and remains a problematic deficiency of Cameroonian literature in its languages."

So let's discuss the facts, and perhaps we can synthesize a more realistic notion of what environment Nnanga Kon came out of.

First, French southern Cameroon in the ''30s, was not remotely modern.. As Andreas Eckhert's Slavery in Colonial Cameroon puts it "Slavery was still everywhere in Cameroon in the early '30s. The Germans did not desire to upset the economic system, and the French followed suit. Moreover, Cameroonians were espected to assimilate to French culture and law as best they could. Their old way of life, so they were taught by the missionaries, had no redeeming featurea".

As such, Cameroonian art, such that it was, was entirely dedicated to producing small decorative items to be sold to Europeans. Yannick Dupraz's Colonial Legacies in Education:: A Natural Experiment in Cameroon lays this out very starkly: "...all education, all art, and all endeavor, was designed [...] to improve things for the French citizens who lived there."

Jean-Louis Njemba Medu and his Nnanga Kon must be understood in the context of this environment. Medu was educated by American Presbyterian missionaries in the Ebolowa region..Afterward, he became a teacher and school administrator employed by the French colonial authority, and he continued in this position until failing health led to his retirement a few months before his death at 64.

If you have not started to pick up on where this is going, yet, there is a reason we aren't reading Medu's book in school like his fellow countryman Oyono's "Houseboy," a staple of postcolonialism.

And that reason is that tbe work is not poco. It is colonial propaganda. Written in tbe language of the common people. It was simply too early in history to be otherwise . Medu was a self-declared "loyal servant to the French Empire," and the book itself tells the story of hapless black Africans being saved by superhuman, benevolent white people with incredible technology - and that's why it is considered sci-fi

Descriptions of the book online may say differently about it's plot and aims, but I do not believe the book is even available in English. The last edition was printed in 1986. I read it in French,, in a translation from.the '70s. I stress that it does not conform to modern sensibilities,

I know that is not the answer you were looking for, heh.