Between 1909 and 1923, Franz Kafka kept what he called his Tagebücher, or “diaries”. At first glance, much of their content is strikingly unrecognisable as diary entries – often undated, penned deep into the night in dense handwriting, with crossings-out, corrections and insertions, now and then accompanied by drawings.

Across these 12 notebooks and two bundles of loose paper, the German-speaking Jewish Prague native interspersed many different kinds of writing: not just records of daily events, reflections and observations, but also drafts of letters, accounts of dreams, outbursts of anguish and bouts of self-torment, enigmatic aphorisms, and all-but-finished stories.

It’s often difficult to discern whether Kafka is registering…