“My mother was a great fake.” That’s Norah, the novel’s narrator, talking about the famous actress Katherine O’Dell. Norah is endlessly asked what her mother was really like. By way of contrast, Norah herself has “always found reality very reassuring”. Take that with a grain of salt.

Actress (Jonathan Cape) is Norah’s loving account of her mother. Katherine, born in 1928, became the greatest Irish female star on stage and screen for a dazzling few years in the 1950s. She owned a grand house in a grand Dublin square, entered a Hollywood marriage with a gay man, had many lovers, shot someone, went mad, never retired, and died at 58. She had refused to tell Norah the name of her father. Norah, soon to be older than Katherine was when she died, is stirred to look into her mother’s life and perhaps discover the identity of her father, when a righteous young woman threatens a biography of the “real” Katherine O’Dell.

Katherine’s life was, as expected, fabulous. Or “marvellous”, as she would say – everything was “marvellous”. Norah remembers life as a series of parties, the huge basement kitchen filled with the famous, full of booze and talk. Sex was secondary to the talky men but still happened. Apparently. The gendered attitudes are heart-sinking. Norah “has a mind like glass” and, over the course of writing about her mother’s life, pieces together fragments of memory and knowledge into a spinning prism of life as it was lived by the radiant, nervy Irish star.

But Katherine O’Dell was not Irish at all. She was born in London and came to Dublin in 1939, when her parents, strolling players, fled the coming war. Katherine boarded in a convent and in summer holidays she acted on stage with her parents, stepping into any role that might be needed on the night.

Anne Enright, spoken about as the greatest Irish living writer, winner of so many major prizes, is masterly. She writes of the “shape of the air” inside an empty house and you know what she means. Actress addresses the nature of reality and authenticity, focusing on the melting, capricious line between the truth and the fake. On stage, Katherine’s genius, her truth (which is fake), allows every individual in the audience to see something about themselves. If she performs herself offstage is she any less real, or truthful? Katherine loves her daughter. She also loves performing loving her daughter. It adds to the depth and infinite variety of the most essential human thing, emotion. Distillation of emotion is the actor’s gift.

Great artists performing onstage can re-fashion our yearning souls. There are superb, undetectable performances in daily life as well, the only difference being the choice, and place, of the act. The witty, self­deprecating Norah, for instance, performs her own long, happy marriage as a counterpoint to her mother’s affairs with dreadful men. Yet her own choice is just as dreadful as any her mother made. Maybe authenticity is just a different kind of act.

The most clear-eyed novel about acting and theatre was Henry James’s The Tragic Muse, published in 1890. It’s been a thin intervening 130 years until now.