From epubbooks.com:
Carson Napier is the first Earthman to visit Venus, and he has to keep alert every moment of his stay in that world of mist and mystery. For its territory is unmapped, its inhabitants strange and he has undertaken to restore a native princess to her lost homeland. In terrible oceans where dreaded sea monsters dwell, in deep forests where fear haunts every branch, and behind the walls of eerie cities where power-mad chieftains plot uncanny schemes, Carson of Venus faces damagers that no man ever faced before.