I don't have too much to say about this work--it's an important topic and probably the first major American study that covers it (originally published in 1916), but I find in-depth discussions of "trade" (without being too hostile, I want to otherwise call it "robbery") between Spain and the Americas to be a bit of a sleepy topic. Studies of social relations, politics, religion, race, etc. are all great, but economics leaves much to be desired.

Nevertheless, the main argument of this work is that the "discovery" of the Americas freed Spain (and Portugal) from their limiting circumstances in Europe. The Mediterranean was dominated by the Ottoman Empire, and there was an enormous shortage of precious metals throughout the continent that made it difficult to do trade with foreign powers (interestingly, Haring finds that the level of interest in alchemy in the late Medieval period and the Renaissance was driven by the same engine that led to European expansion--the desperate need for gold). While little wealth was found in the islands of the Caribbean and modest wealth was found in Mesoamerica, the Spanish found themselves retrieving a metaphorical gold-mine from the Inca, as ransom for the Sapa Inka's life in 1532. This stimulated far more interest in the wealth of the New World, which, throughout the sixteenth century, saw mining centered in Peru. Although there was a decline in wealth exploited from mining in the seventeenth century, it was still a large enough sum to push Spain into a golden age (which also led it to suffer from hyperinflation).

This book has been far surpassed by more recent works, but it's worth reading if you really want to see what the early scholarship on colonial Latin America looked like.