Book Of A Lifetime: The End of the Affair, By Graham Greene

The epigraph to Graham Greene's 'The Lawless Roads' is a magnificent quote from Cardinal Newman: "If there be a God, since there is a God, the human race is implicated in some terrible aboriginal calamity." Just as mad Ireland hurt Yeats into poetry, it was the frictions of faith that brought Greene's novels to life. 'The End of the Affair' is his masterpiece: an astonishing, painfully moving interrogation of the contradictions in a Catholicism he couldn't live without but struggled to live with.

Drawing on his long affair with his goddaughter Lady Catherine Walston (who refused to leave her husband because of her faith), 'The End of the Affair' is Greene at his most pared-down and intimate: he had never written in the first person before. Gone are the tropical locations, the revolutions and gangsters. The narrative scaffolding of Greene-land has been dismantled, leaving us with a novel that gains extraordinary intensity from the narrowness of its focus.

It seems scarcely credible now, but the first time I read the book it seemed much more of a love story than a tale of the ravages of religion. I was 19, living in Paris, perpetually reeling from failed romances. The story of the flawed and floundering Maurice Bendrix and his love for the saintly Sarah was very familiar – her faith stood for all of the confused impediments to love that had prevented me from skipping down the Boulevard St Germain with my current mademoiselle of choice.

The novel inserted fissures of doubt in my adolescent atheism. I remember going to the American Church on the Quai d'Orsay on finishing the book and sitting at the back of the room, waiting for some sort of epiphany. The End of the Affair provides a blueprint for finding a way into belief. Bendrix's sardonic, burly resistance to Sarah's God finally breaks when the weight of evidence becomes too much. But this is not a happy conversion; in his final, bitter prayer – "O God, you've done enough, You've robbed me of enough, I'm too tired and old to learn to love, leave me alone forever" – Bendrix shows that there is no comfort in his new-found relationship with God.

I read 'The End of the Affair' again just before beginning my latest novel, 'The Revelations'. I wanted to write about religion in a way that didn't seem patronising or proselytising. I could think of very few authors who had managed to do this – Peter Carey in 'Oscar and Lucinda', JD Salinger in 'Franny and Zooey', perhaps – but certainly no one since John Donne had engaged so fully with the friction between faith and fornication as Greene. It is hard to write a novel in a Christian setting in such a secular age; 'The End of the Affair' manages to make even the punctilios of Catholic doctrine feel profoundly relevant. Bendrix's hesitant edging towards faith at the end of the novel would give even Richard Dawkins pause for thought.

Alex Preston's 'The Revelations' is published by Faber & Faber