Jake Jameson is an architect. His material is concrete, and the buildings he has produced – community centres, tower blocks, a prison – are utilitarian to the point of brutality. He never managed to make his grandest design: a house of glass that would have risen up from the Lincolnshire moors like something from a dream.

Now he is about to retire, and it seems the lucky trajectory of his life has slackened or snapped. His wife has died, his son is locked in the prison he designed, and, worst of all, his memory has begun to fail him.

Memory is how we are anchored to the world, how we make sense of it and fix our place within it. In this astonishingly accomplished debut novel, Samantha Harvey sets out to explore what happens when a memory can no longer be relied upon.

Jake has Alzheimer's disease. The very architecture of his brain is being unknitted, neuron by neuron. As he struggles to cope with daily life, to remember where coffee cups go or what the woman who sleeps beside him might be called, he grows increasingly obsessed with salvaging a coherent sense of his own past.

At first these key memories seem sturdy but – and this is what makes Harvey's novel so deeply original and captivating – Jake's take is quickly shown to be unreliable. His stories begin to contradict and blur, an effect as beautiful and bewildering as gazing through a kaleidoscope.

Does he have a daughter? At one point she is seen at a bus stop, a pregnant adult; later it seems she died as a child, or perhaps was never born. And the woman in the yellow dress: was she his lover or a more sinister figure from his grandfather's past?

The lyrical power of these shifting and competing narratives is matched by the absolute emotional realism of Jake's own desperate plight: his shame and anger and impotence are devastatingly recorded.

And yet this is not a depressing novel, but rather one so full of urgent life that it rouses even as it terrifies.