Arriving at boarding school with the wrong shoes and a teddy bear in his suitcase, the hero of Elizabeth Day’s fourth novel is the latest in a long literary line of suburban lost boys sucked into the intoxicating orbit of a wealthy friend. F. Scott Fitzgerald, Evelyn Waugh, Patricia Highsmith, Ian McEwan, Alan Hollinghurst and Gillian Flynn have all done it before and we know the story never ends well.