Beyond Numeracy: An Uncommon Dictionary of Mathematics by John Allen Paulos
From the author of Innumeracy, this book explores the beauty and fascination of mathematics. It can be seen as a dictionary (ranging from algebra to zeno), as a collection of brief mathematical essays, or simply as the ruminations of a numbers man on and around his subject. It includes a broad range of mathematical concepts, from the basic to the advanced, from the traditional to such new areas as chaos and fractals, covered in an accessible way.