I would rate Collapse over Germs, Guns and Steel - perhaps this is because I am more interested in how functional systems can fail rather than how they came to be functional.
Some passages that shall remain with me long after I’ve finished the book
Life ends on Henderson:
Did everyone die simultaneously in a mass calamity, or did the populations gradually dwindle down to a single survivor, who lived on alone with his or her memories for many years? Did the last Henderson Islanders spend much time on the beaches, for generation after generation, staring out to sea in the hopes of sighting the canoes that had stopped coming, until even the memory of what a canoe looked like grew dim?
Cannibalism amongst the Anasazi:
Some of the bones had been cracked in the same way that bones of animals consumed for food were cracked to extract the marrow. Other bones showed smooth ends, a hallmark of animal bones boiled in pots, but not of ones not boiled in pots. The most direct sign of cannibalism at the site is that dried human feces… proved to contain human muscle protein myoglobin, which is absent from normal human feces, even from the feces of people with injured and bleeding intestines. This makes it probably that whoever attacked the site, killed the inhabitants, cracked open their bones, boiled their flesh in pots, scattered the bones and then relieved himself or herself by depositing feces in that hearth had actually consumed the flesh of his or her victims.
Failing to neither do the Romans nor do as them:
To us in our secular modern society, the predicament in which the Greenlanders found themselves is difficult to fathom. To them, however, concerned with their social survival as much as with their biological survival, it was out of the question to invest less in churches, to imitate or intermarry with the Inuit, and thereby to face an eternity in Hell just in order to survive another winter on Earth.