Lionel Shriver writes novels. She called one of them We Need to Talk about Kevin. It was scary. Lots of people bought it. Her new book is called Mania. It is set in the near past. It is about the Mental Parity Movement. Under its rule nobody is allowed to be cleverer than anyone else. The word “stupid” is forbidden. Big words are scorned. No sentence (such as this one minus the parentheses) may have a subclause. The vernacular has lobotomised smartphones. Chess and crosswords are abolished. Qualification points are unnecessary for admission to university. Barack Obama is no longer...