1215 is a great book about the Magna Carta - or great charter signed by King John of England in the year 1215 AD in order to placate the Barons.
Taking most of the major clauses in turn it explains the background and reasons for their inclusion at the same time giving a great insight into life in England at the time.
A final chapter covers some of the myths about Magna Carta - from being only about the rights of Barons (OK it was mainly about the rights of Barons!) to being a foundation of liberty (Ok it has a place as rallying point for human rights)
Strangely enough King John soon went back on his word, meaning the immediate impact of the document was very small.
Two snippets - English Law moved from trial by ordeal to trial by jury (whereas most of the rest of Europe rediscovered roman law which use torture on both accused and accuser to get to the truth)
The loss of the French Lands by King John (at one point the English Kings ruled more of France than the French King did!) was a pivotal moment in the development of both England and France. Prior to John, England was ruled by Kings based in France.