My breif Synopsis:
Baron Trump travels to Russia's northern regions in search for a holw in the earth. He finds a tiered well like hole atop of a mountain. He and his dog Bulger, rope down into the whole until they come to a cone like shape in the ground which tapers off into the ground. Baron has to squeeze through the hole by lubing himself up with tar. He and bulger get through the hole. The meet several different underground races in their times down there.
Some are glass like transparent humanoids that wear gowns and hold fans to hide their visible hearts. They cannot lie else their eyes cloud over. They have no time as slight is arbitrarily dictated by a from of current passing through conductive metals in the ceilings, and they have beds all over the place so they can sleep when the metals go dim.
Another race, apparent like ants? who do not use eyesight, but rather braille and braille like communications, vibrations as well.
Another civ is some sort of Ice people who quite literally melt if barron is around them.
You can listen to a librevox recording on youtube for free if you cbf downloading a pdf. the one i listened to was around 4 hours long.