This is a history of code making and code breaking from its inception (Caesar shift cypher) to modern public key encryption and beyond (he has a section on quantum cryptography at the end).
The stories are amazing, more than interesting, and Singh has an exceptional talent in making complex concepts simple to understand.
Not only does Singh tell interesting stories, but exactly when you want it, there is a photo of the machine he's talking about, or the person making the amazing discovery or cracking a difficult code.
My absolute favorite stories in this book of exceptions stories are the story of Rejewski breaking enigma, and of Clifford Cocks inventing public key encryption.
I highly recommend this book to anyone even remotely interested in code making and code breaking.