How did a small bands of Spanish conquistadors defeat the numerically vastly superior Amerind forces in the Aztec empire and the Inca empire? Innes offers a carefully documented, highly readable explanation of the very different characters of Cortes and Pizarro. It's a fascinating read.
Cortes was an educated minor nobleman, whose letters back to Spanish King Charles offer one source for Innes. Cortes defeated the Aztecs by allying himself with unhappy neighbors, and considerable canny political intrigue. When the Aztec leader Monteczuma was killed and Cortes driven out of what is modern-day Mexico City, Cortes promptly fought his way back to power. Cortes may have been brutal, but there is something there to admire in his tactics, if not his world view.
Pizarro, by contrast, was an uneducated, illiterate thug, who lucked into an Incan civil war and was able to seize the person of the Incan emperor Atahualpa, by betrayal. He accepted Atahualpa's offer to ransom himself for the famous room full of gold, but betrayed Atahualpa again and had him executed. I was unable to find a single promise that Pizarro made and actually kept.
My only criticism of Innes' excellent effort is that he is just a shade too apologetic for the Conquistadore mentality. He is at pains to establish its roots in the end of the Spanish effort to defeat the Moors. But unbridled greed is still unbridled greed, and the picture that Innes paints is incredible.
If you want to understand Latin and South America today, I think you must read this book.