The U.S. border with Mexico has become a linchpin in American politics under the administration of Donald Trump. The demarcation line – in many places – is imposing. A wall. A river. In others, just a fence, or line in the sand. And then there’s the mental border, which often differs from the physical one. Families live on both sides. Cultures bleed out and mix. Those are just some of the themes explored in a new memoir by Jean Guerrero.