Markoff recounts decades of work by visionaries, engineers, dreamers, inventors, hackers, and scientists in an arena which he divides into two branches. Artificial intelligence uses machines to replace us. That's not a hit against this form of knowledge: much of what we do, from searching email files for key words for lawsuits to driving cars, can be done better and with less drudgery by machines than by humans.
Intelligence augmentation uses machines to extend what humans can do with our slower, far less linear brains. The World Wide Web is intelligence augmentation as is Apple's Siri. They make us more efficient, smarter, and perhaps more creative using our weak human circuits.
I found it interesting that, as a competent journalist who communicates his subject matter interestingly, Markoff tells the story of the once and future smart machines through the lives and careers of a long array of human subjects. People make these machines and this book consists of their stories.
This just reinforces what I take from his book: the meaning of the coming smart machines will be essentially political. In this society, there is no question that if someone can make a (larger) profit by replacing humans with a robot, that will happen. Likewise, if robots can replace human soldiers in war, that will happen. As we know, this is happening; it will happen more.
But at the same time, we can also choose to use technology to enable more people to live better lives. We don't yet know all the avenues that lead that way, but people will find them.
Markoff envisions the consequent choices being made by individual genius engineers. But human societies are larger than their leaders and larger than our geniuses. People are going to want into these decisions. It will be messy, but it will happen.