As his biographer, I feel obliged to quote John Updike’s wise sayings — among them the first rule in his code for book reviewers: ‘Try to understand what the author wished to do, and then do not blame him for not achieving what he did not attempt.’ Too bad about the gendered pronoun; otherwise, spot on. Rules are made to be broken, though, and when it comes to Anthony Quinn’s Klopp, I have to say I wish there were more Klopp, less Quinn. In the prologue, the author warns us: ‘This book is not a biography of Jürgen Klopp.’ So what’s with the title?

Jürgen Norbert Klopp arrived at Anfield five years ago to take charge of Liverpool Football Club. He brought with him a high-intensity style of play (what he called ‘heavy metal football’) and a singularly seductive persona. Watching Klopp’s Liverpool has been a thrill, the fans rewarded last season with a trophy they’ve been hankering after for 30 years.

Watching Klopp has been equally satisfying. On the touchline he’s a dervish; in pre- and post-match interviews he’s almost obscenely charming — honest, intelligent, sensible, funny. He can’t seem to open his mouth without saying something memorable and downright decent. Which is why legions of people who wouldn’t normally register the existence of a football manager have fallen in love.

Quinn is smitten. I’m smitten. And so is the comedian Laura Lexx, who flaunted her feelings on Twitter:

If I ever met Jürgen Klopp I’d say: ‘Omg if we have a baby we should call it Klipp’, just so he’d raise an eyebrow at me and tell me I’m a moron, and I’d be so naked by the time he’d finished doing that.

Lexx’s tweet went viral and spawned a book, Klopp Actually (published by Two Roads), which carries on in the same vein for 132 pages.

Quinn’s Klopp-love is grounded in solid Scouse fandom. He grew up in Huyton, in ‘an unexceptional house in an unexceptional road’, and by the age of seven, he tells us, ‘football more or less ruled my life’. A year later his father took him to Anfield for the first time. He recalls ‘the eye-popping green of the pitch and the heavy masculine stench of cigars and liniment’. Still passionate about football in middle age, he embraced Klopp as LFC’s saviour. Within 24 hours of that fateful day in October 2015, Quinn was literally dreaming about the newly installed manager; his wife diagnosed a ‘man-crush’.

His book is indeed a billet-doux; but his attention wanders as he riffs enthusiastically on David Bowie and on Robert Aldrich’s 1965 film The Flight of the Phoenix. Luckily he is an engaging and fluent writer, and there’s just enough Klopp content to placate ardent admirers.

The danger in reading a book about a hero is that you might learn stuff you can’t unlearn — such as the fact that Klopp treated himself to a hair transplant in 2012 (and acknowledged it cheerily, telling reporters: ‘Yes, it’s true… And I think the results are really cool, don’t you?’). Or that he had his teeth whitened by the same dentist who worked on the Liverpool forwards Roberto Firmino and Sadio Mané (all three now flash egregiously bright grins). Or that as a young player Klopp once headbutted a teammate in anger.

But he can always be counted on to brush away any misgivings. Remember when he was asked to put his finger on what went wrong during an ugly Champions League defeat in Belgrade? He replied: ‘I only have ten fingers.’