Virginia Evans’s debut novel opens with a letter, dated June 2012, from Sybil Van Antwerp to her brother in France. “Thank you for the birthday card, the fountain pen, and the book, which I started the day it arrived and finished today,” it begins.

There is something revealing about the speed with which The Let Them Theory entered the cultural bloodstream. In an era of increasingly complex conversations around boundaries, healing, attachment styles and emotional labour, the book’s central premise arrives with startling simplicity: let them.