1493 by Charles Mann
You wouldn't think there was another revelatory, perspective-shifting book to be gotten out of the arrival of Columbus in the New World, but 1493 is just that. (You wouldn't have thought that before Mann's last book, 1491, either.) His focus here is on what has been called "the Columbian Exchange": when Europe and America came into contact, the membrane separating two radically different biospheres was ruptured, kicking off a riotous exchange of plants and animals and insects, both micro and macro, in both directions, west and east. Wheat, sugar, coffee, horses and cattle went from old to new; potatoes and tomatoes and tobacco and corn and rubber went the other way; catastrophic diseases went both. With immense energy and curiosity, Mann chronicles what amounts to the birth of a truly global ecosphere struggling to find a new equilibrium. It was a bloody birth. These forces were hugely powerful historical actors, and every trade turned out to be a trade-off too.