The truth is that Dolly Parton defies analysis. She has been a star for more than 50 years, without a hint of scandal and without ever being photographed looking less than immaculate. She is her own special, joyful invention, whether singing about her mother’s love for her in Coat Of Many Colours or writing the ultimate break-up song, The Grass Is Blue.

My favourite Dolly story is about the drummer in her backing band who told her that her stage costume was too flashy. Dolly fired him and bought a drum machine instead. The machine saved her a lot of money, she said sweetly, and ‘it don’t talk back’.

In She Come By It Natural, the journalist Sarah Smarsh tracks Dolly Parton’s trajectory from being reduced to “the punch line of a boob joke” to “a universally beloved icon”. Now, Parton, who turned 75 on Tuesday, commands centre stage, “where women of a certain age historically have gone unseen”. The book was born in the turbulence of US politics in recent years. Not recognising the “hateful, sexist version” of the rural working class propagated by the press during the 2016 presidential election, Smarsh set out to paint a more nuanced picture in a series of pieces for the music magazine No Depression.

Compassionate and clear-sighted, She Come by It Natural catches the power of an entirely self-made woman, one who has endured to see her reputation transformed, her art taken seriously — “an atonement countless women have deserved but never received,” Smarsh says.

It leaves us thinking none the worse of Dolly, and directs one toa treasure house of joy. The time I spent catching up on Dolly’s films and albums, in concert and being interviewed, before writing this review, was a delight. If the present Pope wants to stretch a rule or two and declare her Saint Dolly tomorrow it would be quite all right with most of us.

The book also comes with an autobiographical seam. Telling of Parton’s famously impoverished childhood in Pigeon Forge, Tennessee, and her subsequent move to Nashville to make her fortune, Smarsh weaves in tales of her own trailer-park background in Kansas and her desire for a better life. She includes stories of her mother, who was a single parent, and her grandmother, Betty, who was born the same year as Parton, and who married and divorced six times. The author digs deep into Parton’s lyrical preoccupations that portray the darker side of working-class female experience – “Daddy Come and Get Me” is about a woman who has been institutionalised by her husband so he can continue his philandering undisturbed; in “Down from Dover” a pregnant girl is kicked out of her parents’ house and gives birth to a stillborn daughter alone. Parton’s early songs are, Smarsh says, “southern gothic defences of poor women”.