This is both a gloomy and a hopeful book.
The subject itself is gloomy. A Dark Age is a culture's dead end. We in North America and Western Europe, enjoying the many benefits of the culture conventionally known as the West, customarily think of a Dark Age as happening once, long ago, following the collapse of the Western Roman Empire. But in North America we live in a graveyard of lost aboriginal cultures, many of which were decisively finished off by mass amnesia in which even the memory of what was lost was also lost. Throughout the world Dark Ages have scrawled finis to successions of cultures receding far into the past.
Chapter One, The Hazard, p. 3 - Dark Age Ahead (2004)