In Pursuit of the Unknown by Ian Stewart, 2012, ISBN 978-0-465-02973-0. Subtitle: 17 Equations That Changed the World. This book has a label on the back the says Mathematics, but I think it should be labelled Physics, etc. It is really more about the subjects of the equations than the mathematics. Subjects discusses include Pythagora's Theorem, Logarithms, Calculus, Newton's Law of Gravity, Square Root of Minus One, Euler's Formula for Polyhedra, Normal Distribution, Wave Equation, Fourier Transform, Navier-Stokes Equation, Maxwell's Equations, Second Law of Thermodynamics, Relativity, Schrodingers Equation, Information Theory, Chaos Theory and Black-Scholes Equation.
If you are interested in how mathematics is used in the real world, I think this is a good introduction. It is well written, informative and I think entertaining. Sadly there is no list of books for further reading.
 Purchased from Amazon on 2013-3-7 for $20.51.

Facts on File - Calculus Handbook by Eli Maor. 2005, ISBN 0-8160-6229-3. This a reference book intended for students of calculus. There is a six page historical introduction to calculus. This followed by four sections of reference material. The first is a Glossary that defines many terms related to calculus, trigonometry, analytic geometry and strangely economics and finance. The second section contains Biographies of various mathematicians, third is a section of Chronology that lists significant events in the history of mathematics and finally the fourth section has some tables listing various facts about trigonometry and calculus.
The glossary is hard to read from beginning to end because it is an A-Z dictionary of math terms. It isn't intended to be read that way, but instead as a place for the student to look up terms. The other sections can be read from beginning to end or just those parts that the reader is interested in.