Elizabeth Bishop is the most disruptive and mysterious of modern poets. Disruptive because no one expected a poet of such cool and desolate intelligence to upset the apple cart of 20th-century poetry. Mysterious because it’s still not clear how this happened. How someone who, in James Merrill’s words, undertook the “lifelong impersonation of an ordinary woman” could have dazzled and subverted the modernist canon.

But she did; and still does. In her extraordinary late poems Bishop was not only a defining poet; she was also a radical one. Poems like One Art and The Moose have an eerie double effect. They draw the reader into revelation, but always with a throwaway, conversational tone. This eerie alloy of dark music coupled with a deceptive vernacular was Bishop’s signature achievement. Through it she unsettled the elevated stance of the modernist poet, which plainly irritated her. Through it she kept the poetic self to scale. When Robert Lowell published Life Studies, in 1959, fusing grand relatives with lyric disclosures, she wrote him a letter, her words iced with irony: “I feel I could write in as much detail about my Uncle Artie, say - but what would be the significance? Nothing at all.”

Oddly enough, although Bishop has attracted passionate readers, she has not always had accurate critics. David Kalstone’s early studies, Becoming a Poet and Five Temperaments, remain important. And there have been other careful readers. There is, for instance, a fine oral history. But too often the critique has seemed to portray her as a miniaturist, an artist on ivory. Too often the great poet of Geography III has been diminished by the conversation. Sometimes it has seemed that a radical poet would have to wait for a radical critic.

She has found one. Colm Tóibín’s powerful, unorthodox study of Bishop’s work - simply called On Elizabeth Bishop - reverses accepted critical process. Instead of beginning with a poem and listing the elements that might transform the reader, he begins at the end: with the transformation itself. The transformation, that is, of his life by her language. He holds the mirror of one up to the other. “In certain societies,” he writes “including rural Nova Scotia, where Bishop spent much of her childhood, and in the southeast of Ireland where I am from, language was also a way to restrain experience, take it down to a level where it might stay.”

Therefore Bishop is not just critiqued in this book: she is translated. In a compelling chapter that takes on The Moose, Tóibín shows himself herding the lines and half lines towards his own witness. Bishop opens that poem with a gesture towards her childhood landscape:

From narrow provinces
of fish and bread and tea,
home of the long tides
where the bay leaves the sea
twice a day and takes
the herrings long rides

Describing his own afternoon in Nova Scotia, Tóibín annotates this stanza. “On the first day in the late afternoon,” he writes, “I thought some cataclysm had occurred as I heard a sudden roar of water outside. It was as though a dam had burst or the level of the sea had finally risen to engulf us all. In the matter of a short few minutes the whole bay filled up, vast amounts of water poured in. It was not like a storm breaking or a sudden shower of rain. It was faster than that and almost violent. This was one of the long tides Bishop refers to in The Moose.”

Is this book then an exercise in subjectivity? Not at all. This is critical method. And critical method at its best. This is what was pioneered in William Hazlitt, admired in TS Eliot; this is what makes John Berryman’s essay on Dylan Thomas great and Adrienne Rich’s on Emily Dickinson essential. This is what sorts out the true difference: the competent critic of poetry analyses; the great critic of poetry testifies.

On Elizabeth Bishop is divided into 13 parts. The sections are linked and separate, moving in a sort of lateral creep between Bishop’s poems and Tóibín’s life. An example is the relation between the third and fourth sections. The third is called “In the Village” and considers some late poems against the childhood background. Tóibín provides his own eye-witness accounts of the Novia Scotia landscape, the modest house where Bishop’s mother lived and that noisy tide filling the bay. He writes of Bishop’s “wounded sensibility”.

This might well raise an expectation of a straightforward critical chronology. But the fourth section makes an abrupt detour. It begins with the striking sentence “I come from a house where Time’s hand had also reached in.” Once the reader picks up this rhythm and can follow the swerves from close reading to personal disclosure, there is a sense of having a Virgilian guide: a voice ready to provide his own life as context for the text. This is what makes this book unorthodox, original and deeply effective as literary witness.

Which is not say there are not omissions. Tóibín has a long relation with his subject’s work. His uses this to discuss other writers and artists: Thom Gunn especially, James Joyce in some depth, Marianne Moore and Robert Lowell on the periphery, Tony O’Malley towards the end. They are all part of the argument.

But he seems to miss - or more likely look away from - some other key aspects. A part of Bishop’s work consists in establishing a conversation with canonical practice. The Moose, for instance - as well as being other things - is an abrasive talkback to the sanctity of traditional nature poetry. Instead of the accepted epiphanies of the individual the poem insists on communal revelation - by the passengers on the bus moreover, who don’t quite fit an approved Neoplatonic profile. In the same way One Art up-ends the villanelle. Sestina drenches the old troubadour trobar clus [a style of enigmatic poetry] in magic realism. And so on. I would have liked to read Tóibín’s view on all this.

Then again these aspects are not really in his project: they more likely belong to a different critique. His reading, his studying is done through a different lens: the life her language changed. “I carried Bishop’s Selected Poems with me in my red suitcase when I went to Barcelona in 1975,” he writes. “It had become a treasured book.”

And so begins the call and response: as she writes about the tide in Nova Scotia or the light in Brazil, he answers with a view of the southeast of Ireland or moonrise on the sea at Cush. The book ends as it begins with the shared meaning of place. “This feeling,” he writes, “that we know somewhere, or we knew it and it is ‘live’ and touching in detail is as Bishop says ‘the little that we get for free / the little of our earthly trust. Not much’. Not much perhaps but enough to be going on with. Or perhaps not.”

In this book it is more than enough to be going on with. The close mesh between Tóibín’s growth as a writer and Bishop’s journey as a poet, the eloquent mirroring of place and displacement, and above all the openness to a poet’s language, a poet’s truth put this among the best books on poetry I have read in years. I have no doubt it will become an essential text on her work.