The Egyptians had their pyramids. The Anglo-Saxons had their barrows. And the Americans have their presidential libraries – the chief difference being that the leaders the US venerates are usually still alive at the opening. Lacking a royal family or a state religion, the US presidency has swelled to fill the void, transforming over the decades into a national personality cult, complete with its own secular temples to these powerful men. The latest pharaonic edifice is about to open on Chicago’s south side, where it looms on the skyline as a towering totem to the 44th president, Barack Obama. He...