E = mc2 by David Bodanis

A really neat book about a great subject, well-written, well-executed. Discusses Einstein and many other people involved. Explains the elements of the equation in an engaging way. Is full of interesting asides, such as why WWI ships have their metal used on moon probes (low background radiation in pre-Hiroshima steel). That 1.8 billion years ago, some natural uranium deposits had gone critical because a natural aquifer had slowed neutrons and caused a reaction in Gabon near the Oklo river. It talks about the destruction of the Norway heavy water plant stopping the German A-bomb effort. Numerous excellent references. A very good book - a delight.