21 lessons for the 21st Century (Book Review) 21 Lessons for the 21st Century by Yuval Noah Harari My rating: 5 of 5 stars We live in an extremely complicated world. It’s so difficult to make sense even of the tiniest realm of our lives. Religious dogma, political gambles, economic disparity, an ever-increasing gap between poor and rich, promises and dangers of new technologies like Machine learning and artificial intelligence form the most confusing crossroad in all of the recorded human histories so far.