‘Hiking with Nietzsche’ sounds like the premise of a darkly humorous sitcom or the punishment for an existential crime. Rhetorically ferocious, intellectually conceited and, for much of his life, physically infirm, the 19th-century German sage is not my idea of a pleasant travel companion. Like John Kaag, the author of Hiking with Nietzsche, I went through a Nietzsche phase as a teenager. Unlike him, I have no desire to go back.

Happily, you don’t need to like Nietzsche to love this book. You don’t even need to like John Kaag – and you might not at first. The book begins with condescension: according to the epigraph, a quote of Hermann Hesse, ‘Most men, the herd, have never tasted solitude.’ Kaag disdains ‘beer-drinking Americans’, who gather ‘to eat burgers and watch’ the Tour de France, and compares his fleeced and pillowed neighbour on an aeroplane to Nietzsche’s cowardly ‘Last Man’, for whom ‘safety and comfort [are] the root of all happiness’. But appearances can deceive.

Kaag is a professor of philosophy and a pioneer of philosophical memoir. His previous book, American Philosophy: A Love Story, was about his depression, his divorce and his new relationship with Carol Hay, a fellow philosopher. It was at the same time an introduction to transcendentalism and American pragmatism, to Emerson, Thoreau and William James, by way of a lost library of rare books. Hiking with Nietzsche is just as personal and just as profound. The blurring of lines between philosophy and autobiography is well suited to its subject, a man whose last book, Ecce Homo, had chapters explaining ‘Why I Am So Clever’ and ‘Why I Am So Wise’.

Kaag is an empathetic guide through Nietzsche’s childhood, frustrating love life and eventual madness. He sketches the main ideas of Nietzsche’s philosophy: the death of God and the need to invent new values, the challenge of affirming life despite our suffering, the need for an ubermensch who is able to face it, Christian morality as the ressentiment of slaves, and the fractures within the self. Along the way, there are portraits of bit players – Adorno, Hölderlin, Hesse – as neat and convenient as passport photos.

Yet this book is more than a well-marked trail into Nietzsche’s world. It is an attempt to reclaim his philosophy for the middle-aged. Does he speak now as he spoke to the nineteen-year-old Kaag, whose professor gave him an envelope full of cash and sent him to Basel in pursuit of Nietzsche? The young Kaag stayed in Nietzsche’s old lodging house in Sils-Maria, Switzerland, hiking the peaks with increasing recklessness, starving himself as a form of slow suicide and eventually falling apart. Now married with a four-year-old child, Kaag wants to retrace his steps, to resolve a crisis deferred for twenty years. The messiness of family life means that it doesn’t go as planned.

We are carried along, even those of us who don’t like Nietzsche, by Kaag’s deft storytelling and by prose of such momentum and transparency that one is ambushed by the occasional aphorism. There are glorious descriptions of nature, lakes and mountains, while walking forms a running metaphor throughout the book: ‘Philosophers, after all, have always thought on their feet.’

Like Nietzsche, Kaag separates himself, a man with a wolf inside, from the sheep that surround him. He presents ideas that are, to put it mildly, debatable, as if they were certain truths. ‘Of course you can choose anything you want,’ Kaag writes, ‘to raise children or get married, but don’t pretend to do it because these things have some sort of intrinsic value – they don’t.’ The suggestion is that any choice is just as good as any other, be it parenthood or suicide – a perspective both alarming and unsupported. The culmination is a brutally unfair account of Kant’s opposing view.

This is where things get interesting, as the book has a secret hero. Kaag’s wife, Carol, is a Kantian philosopher who calls Nietzsche a ‘marauding fool’ and his Beyond Good and Evil ‘the stupidest book’. She makes fun of Kaag for caricaturing Kant and finds fault with his account. This reader identified with her. But Kaag knows what he is doing. As it goes on, his book becomes a muted dialogue between husband and wife; it is as bifurcated as the Nietzschean self.

I won’t give away the ending, which involves a roving flock of sheep, and I won’t pretend that I changed my mind about Nietzsche. But I admired Kaag’s journey. This puts me in the awkward position of hoping that he has another crisis, this time solved by a more congenial philosopher, so he can write another book. Cooking with Kant? Bowling with Beauvoir? Line dancing with Levinas? I’ll read whatever he writes.