Leonhard Euler, a mathematician who was born in Switzerland, created a formula in the middle of the eighteenth century that is still the subject of debate, investigation, and even the occasional limerick. The intriguing history of this revolutionary formula—long considered the pinnacle of mathematical beauty—is told in Dr. Euler’s Fabulous Formula, which also explains why it remains at the core of complex number theory. This book, which is in some respects a sequel to Nahin’s An Imaginary Tale, explores the various uses of complex numbers together with fascinating tales from the history of mathematics. Any reader with a basic understanding of calculus and differential equations may understand Dr. Euler’s Fabulous Formula, which is guaranteed to motivate mathematicians for years to come.