His basic argument is that the growing world population and scarcity of resources, e.g. oil, water, usable land, forests, etc, will require us to develop new energy regimes. He's got some global warming in here, but mostly he focuses on the basics of food & fuel (e.g. scarce resources) and our need to innovate and adapt. He uses the U.S. mobilization for WW2 as an example of what is possible.

"As world population has doubled and as the global economy has expanded sevenfold over the last half-century, our claims on the earth have become excessive..."

Here's an NPR interview with Lester Brown