What Was Lost starts off as a straightforward and extremely likeable account of a little girl who sets up a detective agency to honour her dead father. And then the book abruptly cuts from 1984 to 2003. Green Oaks, pallid as it was 20 years previously, is still there. Kate is not. The transition is remarkable. O’Flynn never abandons her wry sense of humour, but as she begins to tease out the connections between the two halves of her brilliantly conceived plot, the sense that something’s missing grows stronger and stronger. The masterstroke of that unexpected shift is to make it feel as if the novel itself mourns the absence of its heroine; the irony, of course, is that her presence is felt on every line

— Spectator

Hugely compelling and inventive, it pulls the rug from under your feet from the very first page – O’Flynn reveals her clues tantalizingly in this poignant story of love and loss

— Costa Prize judges

O’Flynn’s stunning, hugely original first novel was on this year’s Man Booker longlist, and it’s easy to see why – the loneliness of the characters is heartrending and the shopping centre is a character in its own right; a symbol of the age

— The Times

I’m full of admiration for What Was Lost, which skewers our consumer society in all its absurdity and terrible sadness, while deftly interweaving a tender and heartbreaking personal narrative

— Jonathan Coe

A delight to read – poignant, suspenseful, funny and smart. What Was Lost is a moving novel, bespeaking not only the energy and inventiveness of its author but also the power of good old realism

— Jane Smiley, Los Angeles Times

An off-beat, quirky mystery which punches way above its weight. The icing on the cake is the twist which I really didn’t see coming

— Marian Keyes

O’Flynn’s poignant first novel explores bereavement and loneliness, what it is to be invisible and what it takes to be found. Her prose is taut, and the story intricately plotted and compelling

— Telegraph

An exceptional, polyphonic novel of urban disaffection, written with humour and pathos. Kate’s deceptively jaunty diary reveals a consumer–driven society choking on its own loneliness; a ghost story; and an examination of unspeakable loss

— Guardian

It’s wonderful: an uncanny tale that begins in 1984 with ten-year-old Kate, who enjoys pretending to be a private detective until she goes missing. A beguiling novel about disconnection, loss and the anonymity of modern Britain

— Metro

O’Flynn is just the colleague you’d want to be stuck with in a dead-end job

— Literary Review