There is a growing literature of maternal flight: novels about women who leave not just their husbands but also the children they have made. In the real world, men are the more frequent deserters; the connection of the father to family life is seen as contingent, while motherhood is revered as an intrinsic state. This means that women who “un-mother” themselves are doing something impossible: the connection between a woman and her child is not just emotional, but also creational. Joan Barfoot understands the inside-out nature of the logic involved in maternal obligation: “she created these other people and their need for her,” says Abra, the abandoning mother of Gaining Ground, “and now she must fulfil them.”

Abra neglects to fulfil her children or their needs. The novel is rigorously and meditatively about the business of separation, which is also the business of becoming a single and undivided self.

Gaining Ground came out in Canada in 1978, under the title Abra, before it was published in the UK under the current title by the Women’s Press in 1980. This was around the time Barfoot’s fellow Canadian Alice Munro began to write her adulterous, runaway women, whose instinct for freedom chimed so well with the feminism of the day. Abra is not sprung from domesticity by her desire for another man, however, nor does she return to her children, as Leda in Elena Ferrante’s The Lost Daughter does, after years spent regaining what she had lost. Abra is closer to the protagonist in Cathy Sweeney’s recent Breakdown, who has no single answer to the question of why she left her former life: In Japan, Sweeney writes, “So many people disappear that there is a word for them – johatsu. It translates as evaporated people.”

These novels cannot fully resist the question of whether the bolting mother is a monster or a victim of societal expectation. Gaining Ground was written before any of them and, already, Barfoot was wise enough to refuse the terms of the debate: Abra never questions the morality of becoming her true self.

The novel begins with the arrival of a young woman at Abra’s cabin in the woods, nine years after she drove away from her old life. Abra feels her presence as a pressure, an expectation, but can barely remember who the girl is, or who she herself used to be. Then, a moment of recognition – it is her 18-year-old daughter, Katie: “I know her now, and it locks me to her.”

Katie’s arrival tips Abra into a recollection of her lovely, ordered home in Toronto; her marriage, in which there would sometimes be “late movies and making love on the couch and popcorn”; and her two children. Her first baby, a son, provoked a fierce sense of attachment: “I didn’t even want to talk about him, although he so completely occupied my mind, because I felt somehow that talking about him took him a distance away, made him separate, gave a piece of him to someone else.” Her second child seemed less of a miracle: “she was a baby, beautiful, and she was mine and Stephen’s and we had created her, but it seemed natural now”.

The story may be about maternal ambivalence, depression, the loss of meaning, but it always revolves around ideas of truth and pretence. Abra’s life does not feel “real”. Barfoot delivers about 16 different kinds of dissociation without going over her own footprints or saying the same thing twice. The build to Abra’s departure has a cumulative, relentless modernist effect, but she manages to keep it human, or within the human, and we are fully convinced, when Abra sees the cabin for the first time, that this is her “home”.

She has brought no clocks and no mirror, and is at pains to avoid talking to other people. On her first day of digging a vegetable garden her hair proves bothersome and so she lops it off, blind. Abra works to grow food, gather wood and keep herself alive through the long Canadian winter. She thinks only about what is in front of her. The descriptions of work, the natural world and the changing seasons recall the self-reliance of Annie Dillard or Thoreau, who write in a transcendent spiritual tradition. Abra’s revelation is not about God’s infinite majesty, however, but about a kind of unbecoming. She wants to make a life in which she can slowly lose “my name, my memory, the labels I’d used, and so my sense of all words”, to arrive at a place of joy.

When Katie arrives from a world where “there are motives and angers everywhere”, Abra tries to share what she has discovered about “blankness”. She considers the way she once saw her husband and wonders, “Did I make him up?” The answer is that she invented everyone: “I simplified them. And then I reacted to what I had made up, behaved as if what I had invented was real.”

It is hard to find an ending for a book that is trying to be about nothing, so it is considerably to her credit that Barfoot manages an affecting, dramatic conclusion to Katie’s visit. Gaining Ground is a wonderful slow burn of a book and Barfoot’s originality and control remain exciting, nearly half a century on. It is great to see this reissue put the novel at the centre of things, where it belongs.

• Gaining Ground by Joan Barfoot is published by Faber (£9.99). To support the Guardian buy a copy at guardianbookshop.com. Delivery charges may apply.