YMMV / The Master Key

• Unintentional Period Piece: The book is inextricably tied to the turn of the century, because Rob meets King Edward VII, Thomas Edison is still alive, anarchists are assumed to be a threat to civilized society, there are tribes of Africa who have never seen a white man,^note already an anachronism by then and, most importantly, heavier-than-air flight does not exist, and electricity is considered an exciting and wondrous new technology.
• Values Dissonance: That the narrative points out that European explorers often exploited Africans instead of helping them does nothing to mitigate the fact that said Africans are described as completely barbaric and superstitious enough to believe that Rob is a god because of his flying machine, which is one of the few actions he takes early on that the narrative does not condemn.