Muller, a physicist, considers the future of energy use in terms of elementary physics (what is technically possible) and elementary economics (how much it will cost). He frames his highly readable book as a series of explanatory memoranda to a hypothetical U.S. president, covering all the proposals currently on the table and some not yet there and acknowledging that his conclusions and recommendations will infuriate some segments of the public. He is impressed by the high energy density and low cost of gasoline in the United States but troubled by the fact that the country needs to import so much crude oil. He is also pleased with the rapid development of shale gas and the bright prospects for shale oil. He urges the president to focus on energy conservation, hybrid cars, synfuels (liquid fuels made from gas or coal), and smart-grid electricity distribution. He also sees potential for wind power, photovoltaics, nuclear power, grass-based biofuels, and methane-based fuel cells. In his judgment, other alternatives—including electric or hydrogen-powered cars and solar thermal energy—cannot effectively compete.