The Making of Modern Britain is a well-researched book on how the British moved from being Victorians to modern Britains. It looks at political and social change and the causes behind these.
There are enough details to illustrate each point, and to see the changes progressing through the decades. It puts the history we all know into context, and allows a comparison between people of the Edwardian generation as people, not as stiff-upper lipped photographs.
It is important to remember though, that Marr is a BBC man. He criticises the abuse of power by the newspaper journalists in a way that Auntie is protected from, and the monarchy is again generally protected. This is understandable, but makes the book less impartial than it might otherwise aim to be.
Well-worth reading though, and I intend to read The History of Modern Britain, for which this book was a prequel.