This is not a great effort from Edgar Rice Burroughs. There is none of the fantastic worldbuilding that Burroughs is so good at. He does make an odd attempt at a literary trick: he occasionally slips into present tense. There's no discernable pattern to it, and ultimately it's more distracting than clever.

Once again, evil Arab slave traders kidnap the girl. Arabs are an easy stereotypical villain that Burroughs often uses.

There are an awful lot of n-words in this book. (Well, half a dozen or so.) Spoken by the bad guy, yes, but the reason why we're supposed to be disgusted by him using it is because he's using it on Nu, a white man. A paleolithic white man, sure, but a white man.