It’s not the dark hours the insomniac dreads but the clear light of day

The insomniac may come to dread the night’s solitude, but the next day poses the greater challenge. That’s when you are obliged to walk among the rested population and pass for one of them, when in truth most interactions are conducted in a state of self-doubting confusion; when harnessing one’s thoughts is like grabbing at shadows; the right words, if found, won’t cohere into fluent sentences; and dark intrusions from the subconscious flicker up and distract from whichever simple task you’re attempting to complete.

The novelist Samantha Harvey’s first memoir examines a year spent in this condition. It is littered with sharp insights expressed in exquisitely lucid prose but is as amorphous as its title suggests — which is fitting, given how sleep-deprivation distorts our mental framework, revealing the flimsiness of the cognitive structures built by the dormant mind.

Describing a period when she often remained awake for days, she seeks the causes and, where possible, their remedies. The death of a cousin, inner conflict over not having had children — a sadness, and yet she wouldn’t ‘want to make and love something that will die’ — and the EU referendum result: all precipitated her crisis, and (probably) all are irreversible.

But underlying issues might prove tameable, namely an anxious disposition stemming from childhood experiences, lingering resentment towards her father and a nagging scepticism about meaning and reality. ‘The problem with beginning to wonder if everything is a dream or simulation or illusion is that there’s no proof either way,’ she writes. ‘There’s nothing in the world or in your own body, mind or brain that you can point to as proof it isn’t. In this sense, it’s anxiety’s jackpot.’

These are anxious times. Recent years have brought greater honesty about the diverse ways our minds can debilitate us, and this book is timely in analysing a condition that defines our age.