"Fermat's Last Theorem" by Simon Singh

So, is it possible to write an entertaining book about mathematics, in particular, mathematical proofs? Well, it depends. If you have some inclination towards mathematics and the history of science you might really enjoy this book, like I did. It is also great if you want to brush up on some basic math in an entertaining way.

This non-fiction book is about a mathematical problem that dates back to ancient greece, where the Pythagoreans, a secretive "math club" around philosopther Pythagoras, worked on several aspects of number theory. Probably the most important discovery from that time was the theorem about the sides in a right-angled triangle that every kid in school has to memorise: 

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This relation is easy to prove (several proofs are given in the appendix of the book).The more general equation, aⁿ + bⁿ = cⁿ however is not. In fact, for n>2 there is no solution for this equation. Proving this has taken until 1995.
The French mathematician Clement-Samuel Fermat claimed a proof in 1670, but without bothering to actually write it down. It is only due to his apparent genius and other achievements that mathematicians in centuries to follow actually believed Fermat's claim. Ever since, brilliant minds have been unsuccessful in coming up with a proof themselves.
Finally, Andrew Wiles, who had become obsessed with Fermat's last theorem already as a child, and after dedicating his entire career to developing the necessary mathematical tools, solved this problem once and for all in a 100+ page long treatise.

The book takes you through the different centuries and acquaints you with the many great mathematicians who have made significant contributions to number theory and thus provided different pieces to the puzzle. You will enter the oddly fascinating world of mathematical rigour, which yields eternal truths that no other discipline of human thoughts can produce. Mathematical proofs, if done correctly, are valid forever. The pythagorean theorem is a great example for that. Also, you will get to know some of the strangest characters science has known. It is fascinating to see the passion and dedication some people invest in solving problems of "pure thought".

Simon Singh, physicist and journalist, does a remarkable job in recounting the history behind the epic struggle of solving Fermat's last theorem.  If you are interested in learning more about how math works, this book is a great starting point.