Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics, by John Derbyshire
Very engaging account of the history of the Riemann Hypothesis, which is central to prime numbers especially but if proven is known to imply a great number of other results. Got into enough actual mathematics to be a great read for me.
The Equation That Couldn't Be Solved: How Mathematical Genius Discovered the Language of Symmetry, by Mario Livio
Recounts a lot of the history of the development of group theory and its application to proving that general quintic equations do not have algebraic solutions. Much lighter on the math and heavier on the human interest which was okay with me as there are some pretty colorful characters involved.
Fermat's Enigma: The Epic Quest to Solve the World's Greatest Mathematical Problem, by Simon Singh
Covers the history surrounding Fermat's Last Theorem. I read it quite a while ago so I'm hazy on the details but it was written after the theorem was proven and I think devotes two chapters to the story of the proof. This is the story of the proof, not an explanation as such a thing would be way beyond the realm of popular literature.
In a five year period we can get one superb programming language. Only we can't control when the five year period will begin.