The Code Book is full of stories of how codes and ciphers have played a vital role in warfare, politics, and royal intrigue.
The Code Book is an excellent primer for those wishing to understand how the human need for privacy has manifested itself through cryptography. Singh's accessible style and clear explanations of complex algorithms cut through the arcane mathematical details without oversimplifying.
Singh has done a very nice job of demonstrating how deep an impact cryptography has on history. He opens the book by recounting Mary Queen of Scots' conspiracy to have Queen Elizabeth murdered and how she attempted to use encryption to cloak her intentions. It was a very exciting way to open the book.
I want to echo the idea that this is an excellent book for the layperson. You need not be a mathematician to understand and enjoy this book. If you have a casual interest in science and, most importantly, a love of ideas, you'll enjoy this book. I would also recommend James Burke's The Knowledge Web.