Aida Edemariam found the subject of this engaging biography in her own family tree – The Wife’s Tale being the story of her paternal grandmother. And in choosing to excavate and write a family history, she follows a growing trend among biographers reshaping the genre with intimate studies of late mothers, complicated fathers and tragic siblings, from Helen Macdonald and Richard Beard to 2017’s Costa prize-winning biographer, Rebecca Stott.

In Edemariam’s case, it is the life of Yetemegnu, who was born in the northern Ethiopian city of Gondar and died five years ago at the grand age of 97 (or thereabouts: the timeline in the book explains that formal birth certificates weren’t used in Ethiopia in the early 20th century). She emerges as a bewitching and resilient figure whose life-changing moments sometimes intersect with the tumultuous history of her nation. Edemariam’s narrative often expands to cover the bigger picture – Italian occupation in the 1930s, resistance, liberation, political coups, revolts and famine – before contracting back to Yetemegnu’s life.

The opening scene takes place in 1924, when, aged eight, Yetemegnu is married to Tsega Teshale, more than two decades her senior. The wedding scene distils the wonder and confusion of the child bride who feels something remarkable is happening but is barely cognisant of what it means: “The long black cape was lined, the heavy gold filigree around the collar and down the front made it heavy, and it was getting heavier. She hugged herself tight, underneath it. Her stomach was so empty.”

Landscape around Gonderoch Mariam, near to where Aida Edemariam’s grandmother Yetemegnu grew up. Photograph: Fourth Estate/Harper Collins

Her husband is a priest who rises up the ecclesiastical ranks and then becomes a judge under the aegis of Emperor Haile Selassie. She has 10 children by him (not all of them survive and the deaths are wrenchingly described). Despite an often anguished and violent marriage, Yetemegnu fights to clear Tsega’s name when he is arrested for his involvement with the Gojjamé, a resistance group mobilised against Italian occupation whose members were later seen as agitators by the emperor.

Edemariam, a Guardian journalist, says in her acknowledgments that she spent years reading Ethiopian history “before I could begin to understand the world in which she [Yetemegnu] grew up”. What brings this narrative flaring to life, though, is not the rigour of its research but its imagination and novelistic tone; Edemariam’s prose climbs inside Yetemegnu’s memories to inhabit them and bring her solidly, vividly, to life.

The physical world around her too – the look and feel of things, the age-old customs, the seasons around which the book is structured – is invoked with a richness that feels tangible, sensuous: “The dry season wore on… Wild figs darkened in the trees. The peaches mellowed.”

Edemariam began recording Yetemegnu’s voice 20 years ago and some of her words feature in “direct translation”, so this part of the book might be seen as oral history pinned down in prose. It works, for the most part, though the language veers into antiquated phrasing (“I took my leave”; “Would that every day could contain such camaraderie”).

There is a clear sense of discipline to Edemariam’s project of recording Yetemegnu’s life. Unlike those solipsistic “family tree” biographies, where the writer becomes as much the subject as the relative whose life is being resuscitated on the page, Edemariam barely inserts herself into the story.

She describes how her father went to study in Canada and there met his wife (Edemariam’s mother), but she does not dwell on her birth, early life in Ethiopia, or departure. She alludes to a couple of trips back (she now lives in Oxford), but we learn nothing of her possible deracination or her emotional relationship with Ethiopia now. While she hints at a great and deep affinity with her grandmother, she lays down her boundaries firmly. So the book is always about Yetemegnu and the capacity for an “ordinary” woman like her to be bold, brave and unconventional within the constraints of her time and place.

• Arifa Akbar judged the Costa biography award 2017. The Wife’s Tale is published by 4th Estate (£16.99). To order a copy for £14.44 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