I just finished Salt: A World History. Fascinating, and it makes me want to write lots of rules for salt into ACKS.
I recently took a intersting college course, it was a 4000 level history class, Special Topics in History: The History of England from the Stone Age to 1642.
The impact such things as technology (Bronze, Long Bow), climate change (England was once a major wine producing island), migration (talking about a melting pot!) and reglion can have on a civilzation are simply amazing.