Obviously I need to get a copy of Sapiens: A Brief History of Humankind because I loved this book. I can't claim to be well-read in the topic of Homo Deus: A Brief History of Tomorrow, so I'm definitely biased in my opinion that Harari is a genius. Every few pages my copy has lengthy passages highlighted, brilliant bits I just knew I would want to reference when I pitched this book to family and friends later on.
In Homo Deus, Harari holds that now that humanity has all but solved the mammoth problems plaguing it before the 21st century - disease, famine, and violence - it will turn to a new agenda, namely attaining happiness, immortality, and divinity. This is what the blurb will tell you, but the book addresses many more topics beyond the above.
The author writes about our potential future in terms of our recent and ancient past (he is, after all, first and foremost a historian). He explains how humans distinguished themselves from the animal world and came to recognize the human experience and economic growth as the ultimate powers of the recent centuries. Harari then turns to look at where the unstoppable tide of technology and progress may take us in a few decades - whether intelligent algorithms and a genetically upgraded superhuman elite may make ordinary humans obsolete.
His ideas, put starkly, may sound like far-fetched science fiction, but Harari supports his assertions with historical and current evidence as well as deep insights that make his predictions seem chillingly close to prophecy. Even though he states that Homo Deus is meant to help readers explore all possible future routes of humankind, the book still induced an ominous feeling in me the whole way.
One of my favorite passages concerns the belief in a potential scientific "Noah's Ark" which will deliver the rich and social elite from detrimental future effects of climate change, leaving the poor masses to deal with the fallout: Even if bad comes to worse and science cannot hold off the deluge, engineers could still build a hi-tech Noah's Ark for the upper caste, while leaving billions of others to drown. The belief in this hi-tech Ark is currently one of the biggest threats to the future of humankind and of the entire ecosystem. People who believe in the hi-tech Ark should not be put in charge of the global ecology, for the same reason that people who belive in a heavenly afterlife should not be given nuclear weapons. Touché.
And one of the best "food for thought" snippets, in a chapter discussing (among other things) the moral implications of farming animals: If and when computer programs attain superhuman intelligence and unprecedented power, should we begin valuing these programs more than we value humans Would it be okay, for example, for an artificial intelligence to exploit humans and even kill them to further its own needs and desires If it should never be allowed to do that, despite its superior intelligence and power, why is it ethical for humans to exploit and kill pigs
All that being said, the book does have a tendency to ramble a bit. Harari hammers his main points into the reader through numerous repetitions and returns. There are 50 page chapters in Homo Deus, elaborating on and illustrating one single-sentence argument. However, lots of the evidence the author presents is interesting in itself - often it was a historical case applicable to current events - so it never gets boring.