William Prescott 
History of the Conquest of Peru [EPUB ebook] 
With a Preliminary View of the Civilization of the Incas

History of the Conquest of Peru (1959) contains a detailed analysis of the political, religious and social organisation of the Incas prior to the arrival of the Spanish colonisers, and then moves on to look at the story of the conquest and subjugation of the Incan Empire, the largest in South America.