The Collected Prose of Sylvia Plath is an essential yet strangely discomforting volume. It includes writing so apparently far removed from the work for which Plath is remembered – her late poems and her autofictional novel The Bell Jar – that it almost seems to undermine her canonical status. In reality, of course, it does no such thing. Read alongside the works she’s famous for, it offers an insight into how young Sylvia became Sylvia Plath.

Those of us who admire or have been influenced by Plath already know her capacity for self-invention on the page. Peppy letters to her mother form the core of Letters Home, published by Aurelia Plath in 1975. Comprised of letters written between 1950 and 1963, the book opens with Plath’s arrival at Smith College on the eve of her eighteenth birthday and closes a week before her death in Primrose Hill. It’s hard to reconcile the eager good girl of these missives with the savagery of which the late, great poems show their writer to have been capable. There is a swinging of circle skirts and freshly shampooed hair, but the pressure to do immensely well – but not too well – haunts every page (‘Lisa told me about how it is good not to work too hard, but to allot time for “playing with the kids in the house”’).

The Plath scholar Peter K Steinberg knows all this. His comprehensive and fascinating two-volume edition of Plath’s letters, coedited with Karen V Kukil, adjusted what we understood of Plath. This new, deeply researched volume covers years of enormous change. It opens with an eight-year-old’s parable, ‘Winter and Magic’, and closes with a review of Donald Hall’s Contemporary American Poetry, which Plath broadcast on the BBC’s Third Programme a month before her death. In the years between the writing of these two pieces came an attempted suicide, hospitalisation, high school, undergraduate and postgraduate studies, marriage to Ted Hughes, motherhood, arrival as a literary figure and the breakdown of first Plath’s marriage and then her own sense of self. 

Life before thirty, the age at which Plath died, is always full of formative transitions. During this period, Plath was still trying her hand at fiction and various kinds of literary non-fiction, while also writing poetry. Steinberg’s admirably brief preface reminds us that she could be ambivalent about different genres. ‘Poetry … isn’t wide enough for all the people and places I am beginning to have at my fingertips,’ she wrote to an ex-boyfriend in early 1956.

Perhaps some of the material Steinberg has rediscovered would have been allowed to fall away as juvenilia had his subject been someone else. Had she lived longer, Plath herself might have made sure it did. But that’s not to suggest that this is a volume of trivia. Far from it. Only a careless reader could fail to recognise how Plath’s bestseller The Bell Jar, which she first drafted in 1961 and which was published pseudonymously a month after her suicide, is continuous with the pieces gathered here. These include the stories published in the oddly compelling posthumous collection Johnny Panic and the Bible of Dreams (1977), edited by Ted Hughes.

The Collected Prose of Sylvia Plath is an astonishingly comprehensive work, which confirms Steinberg’s distinction as an archivist. At 830-odd pages, it’s also a substantial volume. Presumably to avoid sheer overload, Steinberg has separated the material into four sections – ‘Fiction’, ‘Non-fiction’, ‘Smith College Press Board’ and ‘Book Reviews’ – each of which is arranged chronologically. There are also nearly a hundred pages of appendices, bringing story fragments to the feast. It’s an arrangement that works beautifully, allowing the reader to compare like with like – to weigh up, for example, the mere seven reviews that survive from Plath’s last half-dozen years. 

Mostly, these are roundups of children’s books written for the New Statesman, which tells us something about what it was like to be a writer who happened to be not just a woman but also a mother in literary London in the early 1960s. Still, we see Plath tightening her craft, from the try-hard, slightly overwritten ‘General Jodpur’s Conversion’ of November 1961 to the straightforwardness of ‘Oregonian Original’, published a year later. Her review of Michael Elwin’s Lord Byron’s Wife, from November 1962, is written with a confident ease that makes her intelligence audible. ‘This is jealousy recollected in tranquillity,’ she says of Annabella Byron’s memoir.

Plath’s largely anonymous reports on college events for the Smith College Press Board are less idiosyncratic and were produced earlier in her development. She turned these out as an undergraduate at a time when she was already winning substantial national prizes with stories such as ‘And Summer Will Not Come Again’, ‘Den of Lions’ and ‘The Perfect Setup’. Through examination of microfilms of the local newspapers in which Smith College events were customarily chronicled, Steinberg has matched her ‘letters, calendars and notebooks’ with her published writings. The result is an immensely detailed compendium of these highly disciplined, impersonal pieces, which tells us much about the foreground of Plath’s student life – socials, sport, public lectures.

They also reveal just how hard she was prepared to work on writing, even when the rewards were slight. After all, before she got to college, Plath had already placed four pieces in Seventeen magazine. In the spring of her second year, she wrote ‘Sunday at the Mintons’’ as an assignment for her course English 220b, Practice in Various Forms of Writing. It went on to win the Mademoiselle short-story competition. 

These early stories are conventional in tone and outlook. Even ‘Sunday at the Mintons’’ is a fairly schematic story about an unmarried woman looking after her bullying brother. A foray into surrealism seems to bring him to the sticky end he deserves, yet the story resolves in the bathos of it-was-all-a-daydream. Yet the magic started soon afterwards. By the time Plath was writing ‘Mothers’ (in Devon in 1961–2), everything was in place: eviscerating social commentary, a rebarbative material world of autumn chill and greasy sausage rolls, the scrappy, seemingly inconsequential exchanges through which a friendship is established.

Except there was always the other path. Verse, unlike prose, could be instantly transformative. In summer 1962, Plath broadcast a fine essay on writing poetry and how it differs from writing fiction: ‘How shall I describe it? – a door opens, a door shuts. In between you have had a glimpse: a garden, a person, a rainstorm, a dragonfly, a heart, a city. I think of those round glass Victorian paperweights … You turn it upside down, then back. It snows. Everything is changed in a minute.’