4) Fermat's Last Theorem - Simon Singh (Feb 13 - Feb 15)
This was a history of the famous, titular theorem (actually a conjecture for most of its lifetime, at least to everyone but Fermat) that was finally proven in 1993 by Andrew Wiles. There are two parallel narratives in the book - one relating Wiles' history with the theorem (after discovering it at the age of 10 in a library book and deciding to solve it, and working forward from there ever since), and the other detailing the historical background of the theorem, starting in the 5th century BC (or so) with the Pythagorean Theorem, to Fermat's formulation of the theorem (amidst the insular mathematical environment of the day), to the many attempts at proofs (and progress towards a solution) that followed in the next three centuries. The book is very non-technical, focusing in large part on the people involved rather than the mathematics, and only occasionally even going so far as to describe an equation. It's a good thing, too, because Wiles required state of the art math to solve the theorem - it was, in fact, the ultimate act of synthesis in the number theory field, requiring as disparate a set of fields to prove as modular theory, elliptical curves, and prime number theory.
I found it a fascinating read. I was familiar with the general idea of much of the book - some of the history of the math, etc. But the writer was able to explain mathematical concepts more complicated than I (or anyone) can handle without significant training - his description of the Taniyama-Shimura conjecture (proven equivalent to Fermat's Last Theorem a couple decades prior), for example was simple and high-level enough that I was able to follow along with the progress made on it.
I would highly recommend this book to anyone with the slightest interest in math.