A History of Pi
The Joy of x: A Guided Tour of Math, from One to Infinity
e: The Story of a Number (Princeton Science Library Book 72)
Measurement
Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics
An Imaginary Tale: The Story of √-1
Things to Make and Do in the Fourth Dimension: A Mathematician's Journey Through Narcissistic Numbers, Optimal Dating Algorithms, at Least Two Kinds of Infinity, and More
The Nothing that Is: A Natural History of Zero
What Is Mathematics?: An Elementary Approach to Ideas and Methods