The subject of this book is the "second machine age," in which "computers and other digital advances are doing for mental power — the ability to use our brains to understand and shape our environments — what the steam engine and its descendants did for muscle power." The key technological building blocks for this second machine age are already in place, even if they aren't yet completely mature.

Although these technologies are the culmination of several decades of gradual development, they have only recently reached the threshold of a fundamental phase transition in the way the economy operates. The first part of the book is a walk-through survey of the various technologies involved in the second machine age and the reasons we're just now approaching a phase transition.