Please see the Scottish or Northern Ireland guides for books on the Scottish and Northern Irish Legal System. There are many books on the English and Welsh legal system. There is a selection below but there are many more in the Bodleian Law Library. You can search the library catalogue or browse at classmark KL11.
The UK is a constitutional monarchy. The Head of State is the monarch (not a president), whose duties, functions and powers are conscribed by convention. One of the conventions is that the monarch is politically neutral.
England and Wales operate a common law system which combines the passing of legislation but also the creation of precedents through case law. The laws are established by the passing of legislation by Parliament which consists of the ‘Monarch’, the House of Commons and the House of Lords. The House of Commons is directly elected by the people and the Prime Minister is traditionally a member of this House. The Court System and case law are controlled by the judiciary which is completely separate to Parliament.
See below for a presentation on an introduction to common law and UK common law resources. There is also a copy of the structure of the courts within England and Wales