Quest of the Golden Ape is a science fiction novel by Randal Garrett and Stephen Marlowe first published in 1957.
How could this man awaken with no past-no childhood-no recollection except of a vague world of terror from which his mother cried out for vengeance and the slaughter of his own people stood as a monument of infamy?
A classic pulp adventure of parallel worlds. The other world is on the far side of the sun with the same rotation period so we can t see it. It is a different world; sort of like the world was like when the mongols ruled much of Asia and Europe. Warring tribes, and lots of injustice there from a nasty ruler...
First published in Amazing Stories January, February and March 1957.