It's looking increasingly likely that eventually we'll be clever enough to create artificial intelligence with at least human-level capability. Two likely ways we might do this are 1) to increase the sophistication and coordination of our intelligent algorithms, or, 2) to learn how to simulate the human brain in a computer in such a way that the simulation has equivalent capabilities to the original brain. Hanson puts his bets on the second option happening first, and has written this book to explore what this era will be like as emulated brains ("ems") proliferate and organize into their own cultures.

The book is largely a set of densely-packed, fabulously multidisciplinary extrapolations from existing human historical trends, cultural varieties, and individual eccentricities that attempts to anticipate what this emerging em culture will look like before it is quickly swallowed up by whatever it invents to replace itself.

It is a difficult book to read. Hanson uses discipline-specific jargon and terms of art without pausing to explain them precisely, which often made me feel like I was floating on a cloud of gauzy sociological generalities. It's also often very difficult to figure out why Hanson (or "we" as he sometimes likes to call himself) is making a particular prediction, how confident we should feel about it and why, what the disregarded options were and why they were disregarded, and how the various predictions and their variances might be expected to interact with each other. Often he seems to just be confidently extrapolating from a tiny handful of data-points, not because there's good reason to believe that mere extrapolation has predictive power, but because if you have faith in extrapolation you can predict confidently and predicting confidently is fun. Without much to go on to evaluate his particular guesses, you just have to credit Hanson as being a very smart polymath who is obsessed about this particular topic, and take it or leave it.

This would be an invaluable resource for someone intending to write a book of cyberpunk fiction about this possible era.