Kathleen Jamie's The Overhaul is easy to overlook (as I did when it came out towards the end of last year) because although attentive, it is in no way attention-seeking. This is its power and, although the least vainglorious poet imaginable, Jamie has been scooping up prizes (most recently the Costa award for this collection). Her poetry is to be admired as one might a winter garden for its outline, clarity and light. Her writing is spare: words work hard and are not encouraged to put on fancy dress or show off. Thrift is her strength and an effortlessness that cannot be achieved without effort. One feels that if it were possible to write poems without language, she would be content. What she is after is the unmediated  nothing, including words, must get in the way of what she sees.

Reading the collection is, on one level, the equivalent of taking a Scottish walk, observing birds, deer, sheep and the sea. She lives in Fife and this collection is, one assumes, a Fife littoral. Along the way there is many a Celtic word (some have to be got over like stiles): teind, teuchit, fank, bothy  and it occurs to me that her poems are themselves like bothies: shelters for their readers.

By Jamie's standards, Moon is one of the collection's more fanciful poems. But I love the image of the moon as an elegant traveller with a "small valise of darkness"  not to mention scholarly pretensions, considering the bookcase, encouraging the books to confess. It is Jamie herself who opens up in the end. And as moon and mother collide, there is something biblical about the "unto" in the last line that gives the confession a stiffness that insures against sentimentality.

These poems ask how the world accommodates us and Jamie puzzles over how animals, birds and people know their places. In a wonderful poem, Ospreys  part of a sonnet sequence  she marvels at their long-haul flight from Senegal to Scotland and wonders, as they return to last year's battered nests, whether it was worth it:

Either way,
there'll be a few glad whispers round town today:
that's them, baith o' them, they're in.

The ordinary warmth of this is moving and characteristic.

She applies the same sympathy to the lives of flowers  skilfully avoiding whimsy. In Roses, she considers the brief life of a rose and competition from rival roses: "'I haggle for my little/ portion of happiness',/ says each flower, equal, in the scented mass." In Avowal, she makes a tender comedy of the bluebell's helpless acquiescence, answering all inquiries with an "undemurring yes!" In another excellent poem, she takes the part of a spider, describing it memorably as a "slub in the air's weave". Slub  the accidental knot in the yarn  was not a word I knew and now one I shall cherish.

Jamie has said this is a collection about midlife. If so, it does not describe a midlife crisis but registers the importance of stopping, midstream, to reflect. And she finds a cheering equivalent to the middle-aged person in The Overhaul, the title poem, as she considers a boat named the Lively, above the waterline, awaiting an overhaul.

 but hey, Lively,
it's a time-of-life thing,
it's a waiting game 
patience, patience.

This is advice  as these fine, unhurried poems show  she does not need to apply to herself.

"We're like an audience  standing in the deep cold, looking up, keeping silence, but it's not a show, it's more like watching fluidity of mind; an intellectualism  Not the performance of a finished work but a redrafting." This, from Kathleen Jamie's recent book, Sightlines, is her account of witnessing the northern lights from a ship in the Arctic, but it could also be read as a transcription of the poetic mind in action; the dance of Jamie's words enacts the mind in motion as it moves between the shifting, shimmering processes of nature and art. Jamie's captivating new collection hauls the reader on a strange, profound journey  the poetic equivalent of deep-sea diving at great pressure  throughout which we find ourselves more than usually alive to how language is as moving, as endlessly transformative, as the world we journey through by plane or boat.

Asked about the craft of writing, Jamie has replied that the "trick" is "to make it look easy. Like figure-skaters do." For me, this analogy deftly encapsulates the self-conscious artistry of The Overhaul, which foregrounds the figurative  similes and metaphors abound  as it probes and plays out the tensions inherent in translating human experience in an unintelligible universe into verbal figures of interlaced sight- and sound-lines. Jamie's figure-skating poetics calls to mind the precision-sailing of Gerard Manley Hopkins's "Windhover", the poem itself moving "as a skate's heel smooth on a bow-bend", or Robert Frost's proclamation that "like a piece of ice on a hot stove, the poem must ride on its own melting".

The Overhaul opens on "The Beach", a sonnet (that most enduring of poetic forms) as scene-setter for the poet's unending efforts:

still working the same
curved bay, all of us

hoping for the marvellous,
all hankering for a changed life.

Echoes of Seamus Heaney  who waited until "nearly fifty / To credit marvels"  remind us that The Overhaul, published in Jamie's 50th year, is a "mid-life book".

The "Five Tay Sonnets" explore the form's possibilities for rhythmic vigour, and many of the poems read as musical scores. One of the stand-out poems of Jamie's prize-winning collection The Tree House (2004) had bats

testing their idea
for a new form
which unfolded and cohered

before our eyes

and the form that the poem takes is a vital exploratory device. Michael Longley has paid tribute to the "feel of organic inevitability" of Jamie's poetry, and both poets share a devotional attentiveness to the natural world and the poem as organism. The "curvature of the Earth" (a phrase beloved of Jamie) finds its reflection in the supple curve and fluidity of these revolving shapes on the page and the air.

Thus, "Fragment 1" inquires of the "roe deer / breaking from a thicket":

how can you tell
what form I take?
What form I take
I scarcely know myself
adrift in a wood
in wintertime at dusk

Here, poetic form gives shape to a sense of self-estrangement as the speaker merges, through fluid syntactic ambiguity, with the deer and bodily outlines blur. Accordingly, as humans merge with the natural world throughout The Overhaul, the threat of self-dissolution is pervasive. That Jamie's formal preoccupation involves both art and self is powerfully dramatised in "Hawk and Shadow", a tour-de-force of theme and technique:

I watched a hawk
glide low across the hill,
her own dark shape
in her talons like a kill.

As the hawk's shadow outruns its body, the observing speaker's sense of self disintegrates as soul "part unhooked hawk, /part shadow on parole" dissociates from body. The lines' compulsive rhythmic stress-pulse amplifies the mounting panic, while their dark nursery-rhyme endings vibrate with disjunctive energy as boundaries dissolve to terrifying effect.

For Jamie, language is "where we're at home  our means of negotiating with the world", and throughout The Overhaul different ways of forming experience intersect. The theatricality of the non-human world is drawn out as Jamie's shape-shifting, metaphorical imagination startles the mind awake through unsettling convergences.

Thus, in "The Gather" the rural labourers play their bit-parts as in a nature documentary, "throwing us a grand wave" at poem's end; the bluebell in "An Avowal" is limited to the "small role life / offers you" while "The Galilean Moons" are like "coy new talents /awaiting their call on stage". Jamie rings the changes on words and world; the simile's "like" functioning as the hinge.

In similar fashion, the enlivening energies of translation make possible refreshing linguistic collisions with Friedrich Hölderlin's German reanimated in Scots to compelling sonic effect. In the final poem, "Materials", English and Scots harmonise in the concluding realisation that "a bit o' bruck's /  all we'll leave behind us when we're gone".

Through this dynamic, disturbing collection, Jamie illuminates the mysterious force of poetry in our lives as an unending shadow-play of art and nature, self and soul.