A writer’s career is like any other career: some people get going early, get lucky and go straight to the top; others take a little time to find their way; some of us are forever stopping off, becoming waylaid or detained; and some never follow an obvious path.

The Valley at the Centre of the World is Malachy Tallack’s third book, and even now it’s difficult to know which direction he is going to take. Originally from Shetland, he has returned again and again in his books to the question of islands and isolation. His first, 2015’s 60 Degrees North, was a classic young man’s travelogue, with added grit. His second, an illustrated guide to imaginary and invented islands, The Un-Discovered Islands, veered unexpectedly towards coffee table territory. And now The Valley at the Centre of the World is perhaps his strangest book of all: a novel in which almost nothing happens, and in which everything changes.

Sandy has returned to Shetland with his girlfriend Emma. Brought up in an ex-council house in Lerwick, he now finds himself living next door to her parents, David and Mary, who are crofters in a remote valley. At the beginning of the novel, Emma suddenly leaves to go back to Edinburgh, and Sandy finds that he both belongs and doesn’t belong.

It turns out that there are others in the valley in the same uncertain position: Terry, an alcoholic; townie incomers Ryan and Jo; and Alice, a crime writer, who has retreated to Shetland after the death of her husband, and who is trying to write a book, provisionally titled The Valley at the Centre of the World. “The thing about an island,” reflects an older woman called Maggie, “is that you feel you can know it. You feel your mind can encompass everything in it, everything there is to see and to learn and to comprehend. You feel you can contain it, the way it contains you.” Tallack’s novel is a demonstration that no island – and no person – can ever truly be encompassed.

The action takes place over the course of about nine months – a long gestation, as Sandy undergoes a kind of rebirth. His mother turns up, having abandoned him as a child; he has a brief flirtation with Jo; he reflects on his relationship with Emma; and he learns some crofting basics from David. The tone of the book is quiet and serious, the prose throughout restrained, the pace steady, certainly compared with the lyrical and romantic drift of his earlier books. A typical unhasty description: “He poured a bowl of cereal and set coffee on the hob to boil. He ate at the table, then stood by the window to drink the coffee. From there he could see the valley laid out in front of him, the brown thread of the burn unspooling through the crook of the land.” The point of view is alternating close omniscient, each chapter changing slightly from one person’s perspective to another.

The book is not without excitement and incident: there is a paper trail of diaries and letters, which may or may not teach Alice something about the life of the valley; Ryan and Jo are up to no good; Terry’s drinking leads to terrible consequences. But perhaps most impressive are the careful descriptions of Sandy learning to be a crofter, including one long set piece involving the disposal of a dead lamb.

He felt like leaning over and petting the lamb, then, stroking its tight, greasy wool and rubbing his thumb across its nose, as if he could revive it, a day too late. But he refrained. There wasn’t much comfort to be found in a carcass.

Another source of fascination is Tallack’s rendering of Shaetlan, the Shetland dialect. He goes so far as to add at the end of the book an unnecessary but rather charming note on his use of language.

I have tried my best to get the feeling of Shetland dialect and the local accents, by phonetically replicating as best I can, the grammar, the rhythms and the sounds of the language … I hope the reader will soon find themselves able to hear the voices of the characters.

Indeed one can – though hearing is not quite what happens when reading dialect in a novel. What happens is rather that we voice it, and so in a sense become the characters. This, in the end, is how we enter The Valley at the Centre of the World. Ah’ll laeve dee wi dat thocht, as one of Tallack’s characters might say.

• The Valley at the Centre of the World by Malachy Tallack (Canongate, £14.99). To order a copy for £12.74, go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.