"THE riddle does not exist. If a question can be put at all, then it can also be answered." Presumably this remark by philosopher Ludwig Wittgenstein is a sick joke at the expense of mathematicians, who frequently spend their whole careers clawing at unyielding riddles. And who can blame them for persevering with exquisite torments like the 150-year-old Riemann hypothesis?
It may be an arcane puzzle about the array of prime numbers, but the Riemann hypothesis is also hugely important, and its story has spawned many excellent books. Dan Rockmore's Stalking the Riemann Hypothesis is a fine addition. Much of the content may be familiar, but Rockmore's style, emphasis and language are all admirably fresh, and it is fully accessible to non-specialists. Of course, we are still waiting for the final chapter in the story - that someone proves the hypothesis - but Rockmore is an excellent guide to take you right to the edge of the mathematical map, and he's bang up to date.