This novel is strikingly brave in two ways: first, in the fortitude of its writer, the redoubtable Edna O’Brien, who, aged 88, travelled twice to northern Nigeria, her bra stuffed with thousands of dollars, in order to research this story. With some irony, she ended up staying in a convent with kindly nuns who helped introduce her to its subject: the girls kidnapped by Boko Haram in 2014.