Aida Edemariam’s The Wife’s Tale, a biography of her grandmother who was born in northern Ethiopia more than 100 years ago and married at the age of eight, has won the £10,000 RSL Ondaatje prize.

Given to a work of literature that best evokes the “spirit of a place”, the Royal Society of Literature award counts Edmund de Waal’s The Hare With Amber Eyes and Alan Johnson’s This Boy among its former winners. Edemariam, a Guardian journalist, beat titles including Sarah Moss’s conjuring of iron age Northumberland, Ghost Wall, and Adam Weymouth’s travelogue, Kings of the Yukon, to this year’s prize.

Eidemariam’s grandmother Yetemegnu, pictured in the late 1930s. Photograph: Fourth Estate/Harper Collins

Telling the story of the life of her paternal grandmother, Yetemegnu, The Wife’s Tale: A Personal History draws from research and Edemariam’s interviews with Yetemegnu to write what Ondaatje prize judge and novelist Michèle Roberts described as a mix of “memoir, oral history, fiction and snatches of prayer”. The story moves from Yetemegnu’s birth to her marriage to a cleric and poet two decades older than her, through fascist occupation, the rise and fall of ruler Haile Selassie, revolution and civil war. She died in 2013 at the age of 97.

The biography is a “beautiful, complicated [and] sensual account”, says Roberts. “Her original form and newly minted language create a strong, delicate structure embodying her grandmother’s spirit and will to survive.”

Fellow judge Sabrina Mahfouz said Edemariam’s writing “pulses spectacularly with heart and soul, vividly depicting one inimitable woman centred within the swirling winds of politics, religion, patriotism and change”.

Edemariam, who grew up in Addis Ababa, and is of Ethiopian and Canadian heritage, wrote in the Guardian last year of how she was first drawn to her grandmother’s stories “because of the language and verve with which she told them”.

“She was not able to write, or, until her 60s, to read, and everything was from memory – stories and jokes and dreams told and retold, in an oral culture that prized the ability to do this in the most skilful way possible; what I had were 50-60 hours of tape, of looping, repeating, fragmentary stories, all in Amharic; quite often what I have written is a direct translation of what she said, or as close as I was able, in the cadences in which she said it,” wrote Edemariam. “I also made the decision that, as we were coming from such different points of view, and because, due to my education and training mine carried with it a freighted history of western interpretation, I would try to let her and her world speak for themselves as much as I could. Though I am still present, of course, having translated, written down and/or chosen every word.”