The Code Book, Simon Singh, Anchor Books, New York, 1999

If you have never read a book by Simon Singh you are missing out; who could resist the Simpsons and their Mathamatical Secrets? Singh is a a PhD (Cantab) in physics.  I discovered the present book when I was looking for a text for an Honors course in cybersecurity.  If you want an overview of cryptography from Herodetus to qunatum computing, there is no better place to start.  Writing a summary of this book would be tough as it is itself a summary.  If you have any interest in cybersecurity or cryptography you will enjoy this book.