Michael Stewart 
Modern Forms of Government [PDF ebook] 
A Comparative Study

Originally published in 1958 and written by a serving M.P. this book discusses the nature and purpose of political activity in the Government of Britain, the Commonwealth and the former British Empire. As politics is closely connected with history and economics, the book makes reference to these subject areas, but in a way that is only necessary to give a lucid introduction to the political problems of the 20th Century. The book was written in such a way as to be particularly useful for the introductory study of government and politics.