The Independent: "It's this duality at the heart of friendship that drives the novels."

This is the third of Elena Ferrante's Neapolitan novels, a series of four books following two friends from their childhood in a poor Naples neighbourhood far into adult life, until one of them – Lila, the "brilliant friend" of the first book's title – decides to disappear "without a trace".

It is left to Elena, an author with Greene's splinter of ice lodged firmly in her heart, to do what she always promised she never would: put her friend in a book, in an attempt to understand not just her, but the two of them.

Book two – The Story of a New Name – ended with Lila fleeing from her abusive marriage and good job running a fashionable boutique, and working in a sausage factory on the outskirts of the city. Meanwhile Elena, having written a novel almost by accident, and found herself a succès de scandale, is living the life of a public author, riding high on the revolutionary wave of the late 1960s.

That, of course, is the barest summary. The books come with an index of 50-odd characters, from 10 families, most of them from the neighbourhood, and believe me: you need the help it gives. The story is densely plotted, and its author not much given to description or digression. Ferrante is an expert above all at the rhythm of plotting: certain feuds and oppositions are kept simmering and in abeyance for years, so that a particular confrontation – a particular scene – can be many hundreds of pages in coming, but when it arrives seems at once shocking and inevitable.

The student rebellion of the last book is now spilling over into industrial disputes, and Lila – so cocksure and eloquent – finds herself at the forefront of the workers' movement at her factory. It's not just the owners she's up against, however. They are under the thumb of the Camorra, the criminal organization that reaches its corrupt fingers into every corner of the city, and this brings Lila back face to face with her oldest enemies, the Solara family that rules the neighbourhood she can never quite escape.

What Lila lives, Elena writes, reaping writerly kudos for her articles in political journals, while feeling that she is somehow exploiting her friend: "Her shadow goaded me, depressed me, filled me with pride, deflated me." It's this duality at the heart of friendship that drives the novels, but what makes them so formidable is that the duality isn't stable – the two women are always encroaching on each other's turf, always threatening to upset the balance of power. "Every fixed point of our relationship sooner or later turned out to be provisional," Elena writes.

Crucially, the length of the books allows for repetitions and oscillations. Whether it's work, family, friends or sex – and Ferrante, perhaps thanks to her anonymity as an author, is blisteringly good on bad sex – our greatest mistakes in life aren't isolated acts; we rehearse them over and over until we get them as badly wrong as we can.

- Jonathan Gibbs