Dan Brown, author of The Da Vinci Code, recommends The Golden Ratio: The Story of Phi, the World's Most Astonishing Number by Mario Livio (Broadway, $24.95).
Granted, 1.6180339887 may not look particularly ''astonishing'' at first glance, but don't be fooled -- it plays a critical role in the magic of the Mona Lisa, the grandeur of the Parthenon, the beauty of the nautilus shell, and yes, even the enduring enigma of the Great Pyramids. Still not impressed? Try saying that after reading The Golden Ratio. With plenty of diagrams and photos, Livio unveils the history of the remarkable number phi (pronounced ''fee'') in such a way that math buffs and math-phobes alike can celebrate the wonder. Be forewarned: You will never again look at a pyramid, pinecone, or Picasso in the same light...to say nothing of your own naked body.