Most people probably know 1492 as the year Columbus "discovered" America. Charles Mann's 1493 discusses the oft-neglected implications of that event. That, as a result, Europeans ended up colonizing much of America is known, but this was only the tip of the iceberg of how the world changed.
Whole ways of life in all corners of the globe were ravaged by disease that only spread because of this meeting. Whole populations found salvation through vegetation that was denser and could therefore support more lives. New additions to global trade would destroy the vibrancy of some communities, while prospering others.
Even though Columbus' journey is so well-known, I've definitely come away from the book thinking that the implications of that event are underrated. Whole societies around the world changed what they grow, what they eat, what they wear and what they celebrate, and they may not even know. The irony is that many attempts today to protect cultures from globalization are often protecting the results of the globalization that ensued following that trip, without even knowing it today.
The book is a must-read for history lovers. The rest of you might find it rather long (almost 600 pages) and too detailed.