Physics Today has a great article about the structure and economics of today's electrical grid in the US, as well as some historical perspective. Aside from a flippantly wrong statement in the intro ("volatile market prices have essentially been allowed to move in only one direction—downward" -- ever hear of California?), the article abounds with facts & figures. It also discusses the future of electricity in the US, such as distributed generation and intelligent grid technology, though they caution: "a large and growing gap exists between the performance capability of the electricity system and society's needs and expectations."