Without calculus, we wouldn’t have mobile phones, TV, GPS or ultrasound; we wouldn’t have unravelled DNA or discovered Neptune or figured out how to put 5,000 songs in our pocket. Though many of us were scared away from this essential, engrossing subject in high school, Strogatz’s brilliantly creative, down-to-earth history shows that calculus is not about complexity, it’s about simplicity. It harnesses an unreal number – infinity – to tackle real-world problems, breaking them down into easier ones and then reassembling the answers into solutions that feel miraculous. Strogatz is Professor of Applied Mathematics at Cornell University.