It seems to have changed since the first time I read it, in many ways. But here's one thing I noticed that I think may be an in-joke.
The story so far: our hero Gordon King is lost in the jungles of Cambodia, and takes shelter in what he identifies as a ruined temple of Siva.
... A few feet below him was a stone floor, and he could see dimly now that the chamber extended the full breadth and width of the tower. In the centre of the apartment rose something, the nature of which he could not distinguish; but he was sure that it was inanimate.
... Turning toward the object in the centre of the room, King quickly identified it as the symbol of Siva and realised that he was in the Holy of Holies.
So King identifies something that rises from the middle of the floor as a symbol of Siva. Siva has a number of symbols, known as the Lingam, but Burroughs doesn't specify. Which suggests to me that either Burroughs had no clue as to what this linga was, or he knew very well but it's too rude to be published in 1933.
When I first read it I had no idea, but thanks to my brief flirtation with Hindu theology and religious art, I would guess that the 'symbol of Siva' that King saw was a stone cylindrical pillar with a rounded top; amongst it's interpretations is the obvious one as a phallus.
Hindus don't immediately read the lingum that way (I'm told) but Westerners historically have. Which makes me think Burroughs is making an in-joke which anyone who'd read the same secondary or tertiary sources he had would get. And you can't go wrong with a knob joke.
If my overly close reading of a 30's pulp novel throws out any other interesting factoids, I'll be sure to share them here.
 Obviously it's me that's changed, not the book. But my changes are invisible to me.
 Aka Shiva