Synthetic Worlds provides a good explanation of why social spaces constructed in software will be an important part of our future. But first, Castronova takes the time to give us a feel for what it's like to spend time there, so that we'll understand the inhabitants and what they do while online.'s
Castronova has a very engaging style; I particularly liked the way he keeps the reader apprised of the roadmap he is following and how each chapter and major section fit into the exposition. Castronova is an economist, but he didn't get into this subject expecting to prove an an economic theory—he was just playing games. After he had spent a significant amount of time in several social games, he thought of writing a tongue-in-cheek report on the economies he'd visited. But as he gathered enough data to lend verisimilitude to the joke, he found more and more depth to the real economic interactions going on inside the worlds and in external sites where people were selling in-world artifacts and identities for significant sums. He did eventually write the paper, though from a more serious viewpoint than he had originally envisioned. Within 6 months, it ended up being on of the most read papers available from SSRN, a major repository for serious academic work.
Since then Castronova has been the go-to guy for a serious social science view of these game worlds. He wrote this book to explain what he has learned. His most important conclusion is that the economic and social consequences of what transpires within these systems is real, and so it doesn't make any sense to call them virtual worlds. Not virtual reality, not virtual economies, not virtual goods, not virtual interactions. The interactions are real; the goods have value in the real world; the economies work just like the real world and they trade goods, services, and money across borders with real world economies. It's a real reality and events there have real effects on the inhabitants and everyone else in the same way we can be effected by the weather in the Gulf Coast or a fire or an earthquake in the Far East.
As Moore's law continues to increase computational power, these worlds will become attractive to more people, and more people will spend increasing amounts of time and productive effort there. Read Synthetic World for a glimpse of how it may effect you.