Two Yorkshire schoolfriends, fed up with their Muslim families, schools and narrow lives, fling themselves into religion and encounter varieties of superstition, lip service, lukewarm belief, devout orthodoxy, fundamentalism and jihadism, which has its own subsets of dreamers, talkers and doers. A radical sermon leads the girls to exchange internet confidences with a kind, motherly woman who urges them to help in her Syrian orphanage. Every step of the way, Khair’s gentle humour anticipates and outmanoeuvres the ready prejudices of his characters and readers, indulging and sparing neither. Without melodrama, hardly raising his voice, he leads us through setbacks and disillusion before we and the girls realise that their friend’s job is really to recruit suicide bombers and brides for Isis emirs. Characters and readers alike, we are all soon engulfed in terrifying emotions and scenes. At the heart of this profound, loving book is an insight that deserves to be memorised: “When goodness wants to become pure and alone, that is when it turns evil, truly evil; not the grubby evil that it has tolerate in order to be goodness, but Evil itself.”

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• The headline on this article was amended on 18 April 2017 to correct the spelling of Tabish Khair.