e: The Story of a Number, by Eli Maor

e is a transcendental number approximately equal to 2.718. It is the limit of (1+1/n)^n as n goes to infinity. If you have forgotten your math or were never inclined to learn it, you nevertheless will find this book a manageable albeit often intellectually challenging read. It charts a course through early mathematics. I did not know, or forgot, that the Greeks did not deal with 0 or negative numbers. Their entire system of mathematics was based on geometric proofs and you cannot have a line with 0 or, worse, a negative length. Never mind irrational numbers. Maor brings us through the first documentation of logarithmic functions and the calculus (Newton vs. Leibniz). Much of modern mathematics is built on a foundation of the idea of limits or, more particularly, solving series whose limit is infinity (like the one above). This number, e, is found everywhere and Maor takes us to many of those places. It is not only a mathematical construct, it is grounded in the physical world, not unlike pi. You see it in the designs of seashells, architecture and the banking industry. But more, the book reads not as a mathematical text although there is a bunch of that in there – it is a history book. And, for me, it frames the physical and philosophical world in a different way. It’s been sitting on my shelf for a long time; I’m glad that I finally read it.