The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography; by Simon Singh.

It is rare one comes across a book of this calibre written for lay readers, so very informative and so good in its level of intelligence that borders on testing.

In discussing codes he goes into history and discusses various codes used historically until one reaches Enigma and realises why it was so prized as to have British intelligence and government risk loss of many lives rather than allow the enemy to suspect that they had in fact cracked it or obtained a key, a variation of each having happened during the war.

Then there is the part about Elizabeth I obtaining incontrovertible proof of Mary, Queen of Scots involving herself in plots to murder her and subsequently the ordering of execution of the latter of necessity, unlike the popular misconceptions about the reasons.

A must read for anyone even remotely interested in any topic touching - whether practical application today or historical significance or simply an intellectual challenge. ”