It took me the better part of a week to read 1491: New Revelations of the Americas Before Columbus (Charles C. Mann, 2005), but it was well worth the investment of time. It looks at new archaeological discoveries, especially over the past 20-30 years, that render most of what you learned in school about Native American life prior to European contact wrong. (Incidentally, if you have kids in school now, they're still learning all the wrong things you were taught, because the textbooks haven't caught up with the current state of science and history.)
To oversimplify incredibly, the Americas were much more densely populated, and therefore subject to much more intensive agriculture carried out by sophisticated cultures, than was previously thought. So the marvel of Native American cultures isn't that they lived in some sort of Noble Savage state of harmony with wild nature, but that they found ways to shape their environment to create a generally stable equilibrium allowing them to sustain large populations without ruining the land--in other words, rather than looking back on pre-contact America as a Garden of Eden we proceeded to destroy, we can learn lessons for our own complex, densely populated societies.
So. A highly recommended book, if you're interested in anthropology/history/climatology/ecology/etc. Very much in the Guns, Germs & Steel interest area.