Last May, just before Louis van Gaal was confirmed as the club’s new manager, a man from the BBC asked him what he knew about Manchester United. “That is a stupid question, I think,” Van Gaal replied. “It is a stupid question.” I’m with him: it is a stupid question. Questions, stupid and not so stupid, and Van Gaal’s response to them, are at the heart of O, Louis.

The book, translated by David Doherty, is very good but it is as much about its author, Hugo Borst, as it is about Van Gaal. Its success is largely dependent on whether the reader can find Borst as interesting – as engaging, as irritating, as quotable, brilliant, monstrous and human – as his subject. The answer to that changes from page to page – yes, no, maybe, no, yes, maybe, no, no, Jesus no, no, maybe. It’s like reading about a match that goes into extra time and endless mucky replays, between Borst and Van Gaal or, more accurately, Borst and Borst. Borst, the Van Gaal lover versus Borst, the Van Gaal hater; Borst, the man who wants to be Van Gaal’s best friend versus Borst, the man who wants to annihilate Van Gaal; Borst, the gobshite, versus Borst, the astute, passionate, sometimes brilliant, football writer. It’s a great game for the neutral. But those of us who love our football know that there is no such thing as neutrality.

We already know Van Gaal – or think we do. He goes back. Before arriving in Manchester, he’d managed Ajax, then Barcelona, twice, the Netherlands, twice, AZ and Bayern Munich. As a manager or head coach, he won the Dutch Eredivisie four times, La Liga twice, and the Bundesliga; he won the Uefa Champions League, with Ajax, and was runnerup twice, with Ajax and Bayern. He was the World Manager of the Year in 1995.

Yet he arrived in England like a new thing. He arrived before he’d even arrived – if that can make sense. He was an immediate genius, before he’d selected a starting 11. He was the man who saved Manchester United, months before the current season started. His reputation was enhanced during the World Cup when he replaced Dutch goalkeeper Jasper Cillessen with Tim Krul for the penalty shootout against Costa Rica. There was a touch of magic about Van Gaal. His players clearly loved him. Robin van Persie flew through the air for him.

He’s in Manchester now and, with his dark suit and clipboard, he looks like a wedding planner. But the wedding isn’t going to plan. The groom’s a twit, the bride’s mother is drinking her gin by the neck, and the Tom Jones covers band has turned up without a singer. But he’s still Van Gaal. We know the face, the history, the accent, the arrogance.

We don’t know Hugo Borst. He’s a Dutch football journalist and a lifelong supporter of Sparta Rotterdam. It was at their stadium, Het Kasteel, in 1978, that Louis van Gaal “first appeared” to 16-year-old Borst. He became a journalist at about the same time that Van Gaal became a coach. They were close – Borst thinks – for a while. Then there was a falling out, massive on Borst’s part, perhaps not even remembered on Van Gaal’s, when Van Gaal accused Borst of giving his phone number to another journalist. This book can be read as revenge and self-examination.

I grew up Catholic, so angels appearing to fresh-faced teenagers are always half-expected. This angel, Van Gaal, “had all the mobility of a slug on sandpaper”. Yet “there was a whiff of the sacred about it. There’s something spiritual about Louis van Gaal, just like the Dalai Lama, Charles Manson and Stephen Fry.”

It is the pat and the put-down, the young lad’s perspective and the middle-aged cynicism, and the inclusion of Fry’s name, that make that last sentence appealing. Moments like it are a large part of the book’s fun – and savagery. If there’s going to be a fight between a hugely successful football manager and a journalist, most people will want to hold the manager’s coat. But it’s the journalist who’s doing the writing here. He’s unfair, unbalanced, maybe unhinged, and often nasty. He keeps referring to “our Louis” and “the great man”. But he’s also funny, passionate, probably honest, and a bit of a winger with the words. The final World Cup chapters are glorious. I’ve read excellent books about football before but never one that I found unsettling.

Football journalism is clearly a blood sport in Holland, so much of what is written and cited in this book is shocking. Assessments of Van Gaal by other journalists and, among others, a spin doctor and a psychiatrist – also a star of the TV reality show, Holland’s Worst Husband – are often close to cruel. Botox gets a mention. So does Stalin. And there’s a short account of a phone call between Van Gaal and “the depression-stricken goalie”, Robert Enke, that left me wanting to choke Borst.

The Van Gaal of O Louis is not the Van Gaal we’re getting to know on Sky Sports and Match of the Day. On 7 November, he said: “I feel, myself, very lousy for the fans firstly, but also for the board because they have a great belief in me and my players and my staff, and when you have 13 points out of 10 matches, you are not doing well.” It is impossible to imagine the Van Gaal of O Louis admitting to such vulnerability, if that is what he was doing.

It brings me back to questions, and journalists, and how people such as Van Gaal should engage with them. Discussing the manager with a Dutch politician, Borst suggests that “media training is a good way of learning to avoid pitfalls with journalists”. It’s the most disturbing sentence in the book, and it leaves me hoping that Van Gaal isn’t feeling too lousy.

• Roddy Doyle co-wrote Roy Keane’s The Second Half (Weidenfeld & Nicolson). O, Louis is published by Yellow Jersey.