This is a nice little book about the history of mathematics and the 350-year quest for the proof to Fermat's Last Theorem. It was written by the fellow who wrote the BBC / Nova TV special on Andrew Wiles, but includes a lot more information than a one-hour show could. It does a nice job at hitting many of the high points of mathematical development from Pythagoras to modern day, including the "discovery" of zero, then negative numbers, then imaginary numbers, techniques for grappling with infinity, Turing-computability, and Godel's incompleteness theorem. It doesn't attack any of these in great depth, but it does provide a nice historical perspective while remaining about as accurate as a lay book can do. It also does a nice job of illustrating the near-hubris required for Wiles to lock himself in a closet for eight years in order to solve a problem that had eluded mathematicians for centuries. Mathematicians will enjoy the panorama; non-mathematicians will likely find the introduction to some of these obscure concepts accessible and enjoyable. Also by this author: The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography .
(Recommended to me by: Stuart Marks.)