If you’re a fan of Elena Ferranti’s novels, the news that her Neopolitan quartet was coming to the National in a double bill would probably have had you rushing for tickets. Given that 10 million copies have been sold in 40 countries, that's likely to sell a lot of tickets. Those without any prior knowledge of the books might at first struggle to make sense of the tumble of happenings as April de Angelis’ fearless adaptation doesn’t attempt to simplify the winding plot which spans almost 60 years, condensing it into five and half hours (in two plays) with a cast of 30. But it’s well worth any initial confusion. If the novels have the edge when it comes to depicting the raw intimacy of all those individual lives, the plays have the power to paint a truly panoramic picture of post-war Italy and a profoundly human portrayal of the emergence of feminism as we know it.

‘Until we write our own texts, we won’t know who we are,’ declares Lenu, now a successful writer who has spent a lifetime battling with a sense of inferiority to her darkly determined childhood friend, Lila. Niamh Cusack and Catherine McCormack give unrelenting, complex performances as Lenu and Lila, whose strikingly different personalities and sometimes savage friendship drive the drama.

The show opens with Lenu (Niamh Cusack) in the vast empty stage of the Olivier, closing her laptop before crouching down to open a package that contains the dolls that belonged to her and Lila. From here we step back in time to the poverty, violence and love played out on the streets of Naples. Both women have been born into working class, patriarchal families where violence against women is normalised and few girls continue their education. However Lenu manages to get help to buy her books, eventually working and marrying her way into the academic middle class in Florence while Lila who has married a local man very young fights her way through oppression and tragic loss. For Lila, feminism is not a theory, it’s a visceral reality. Moments of trauma, such as the rape on her wedding night are powerfully portrayed by the character losing contact with her body, her dress taking on life as a puppet while she lies motionless, crumpled in a heap until it’s over.

There is plenty of dance and music at times of celebration which lightens the mood and delineates the changing decades as well as comic turns from the cast, in particular the adults playing Lenu’s children and the brooding matriarch Manuela played by Emily Mytton. Having transferred from the intimate Rose Theatre in Kingston, to the huge space of the Olivier the scale is used to highly dramatic affect. The streets of Naples and the interiors of Lenu’s adult life all take place in the spaces created between stepladders that rise and fall, silently sliding into new forms, with huge projections on the walls and stunning lighting design by Malcolm Rippeth. I imagine being closer to the local street scenes at the Rose Theatre would have made it easier to engage with all the characters initially but the sight-lights are so good in the Olivier, it’s not too much of an issue.

The minutiae of the inner and outer life of these characters is what keeps the page turning in the novels but the epic scale of this production touches us by zooming out from the individuals whose troubles become mere drops in the ocean of history as decades fly by. We are given the space to reflect on our own lives, the friendships that shape us and the choices we make that start the roulette ball rolling.