The Conquest - Robert Pritchard - Bog

Cristobal arrived in Buenos Aires determined to make his fortune, but when instead he loses everything, he decides to join the army on the verge of the final campaign against the natives of Patagonia. In pursuit of the battle that will make Argentina supreme, they push deeper and deeper into the wilderness, encountering stranger and stranger phenomena. Cristobal deserts to join the natives but must flee into a hidden kingdom in the mountains that may be in another history, going farther and farther beyond our reality, until he must confront the ultimate choice.