Readers of Dangerous Hero – the unauthorised biography of Jeremy Corbyn, by veteran author Tom Bower – will be keen to note that while there is a picture of Bower and Corbyn together on the back cover of the book, the author says he never met the Labour leader.

Equally important: it seems hard to imagine, but according to Dangerous Hero, "Momentum members in local branches were empowered to remove Blairite MPs" in constituencies including Mansfield and Hastings, which aren't held by Labour.

Readers will also be interested to learn of the existence of two "social media websites", one called "Aaron Bastani" and the other called "Novari".

Then there's the 30-year old "bisexual republican" Cat Stevens, not to be confused with the 70-year-old Father and Son songwriter Yusuf Islam; Bower is in fact referring to the now 33-year-old Labour MP Cat Smith.

Laura Alvarez, Corbyn's third wife, prefers to go by that name. Bower, who repeatedly suggests that the Labour leader is a misogynist, calls her Laura Corbyn.

On the morning of the EU referendum result, Bower tells us, Corbyn got up late and was "seen laughing over breakfast with his team". Although, as Michael Segalov pointed out on Good Morning Britain, two minutes of internet research leads you to footage of him being interviewed by the BBC at 7.29AM and ITV at 8.08AM. Perhaps the man dubbed "one of Britain’s leading investigative authors" by the Mail on Sunday just has a particularly puritanical definition of what constitutes getting up late.

Dangerous Hero is full of many more factual errors. This is not a new phenomenon. David Runciman described Bower’s book on Tony Blair as "both error-strewn and sanctimonious".

Then there’s the question of originality – what’s less easily debunked in Bower’s book is not original. As Stephen Bush pointed out in the Observer, anyone who has read Rosa Prince’s Comrade Corbyn – or, indeed, a newspaper – will have heard about Jeremy the young hard leftist, the bad student turned political animal, forever attending meetings on some long forgotten imperial outrage, eating cold beans out of a can for dinner and ignoring his wives.

Bower makes a big scene about how he was once a communist ("Tommy the Red", they called him, though we’ll probably need to do a fact check on that) and, as such, knows how the hard left work.

Of course, the picture is never clear. One minute Corbyn is a Trotskyist, the next he’s a Stalinist, the next he’s a socialist. One minute he’s an idiot follower who never read a book in his life, the next he’s a scheming tactical mastermind who’ll inevitably turn Britain into Venezuela. Bower is obsessed with the idea that Corbyn never reads – something friends and colleagues of the Labour leader insist is simply not the case.

On the subject of antisemitism, Bower includes every already well-documented suggestion that the Labour leader might have a problem with Jews, from his instinctive defence of a clearly antisemitic mural to past associations with people the author describes as "Holocaust deniers, terrorists and outright antisemites".

Coming more than halfway through the book, though, Bower’s chapter on "The Jew-Haters" is a broadside whose intensity has already been matched by the author’s fury at Corbyn’s haphazard approach to his personal finances and his insufficiently fervent commitment to Arsenal Football Club. In taking on this subject, Dangerous Hero – along with much of the British media – equates any dialogue with groups like Hamas and Hezbollah to be tantamount to treason, and shows no real desire to illuminate the history of the Israel / Palestine conflict beyond the idea that any criticism of the state of Israel is de facto antisemitic.

Meanwhile, the way the author writes about Corbyn’s Islington constituency and its immigrant population is frequently problematic. "In his world, immigrants’ interests were paramount," Bower writes, as if the right and proper place for the MP's "ethnic constituents" was at the back of the line. Those "interests" were often, Bower says, criminal – a further judgement from on high.

This is all part of the endlessly shifting nature of Bower’s attack. If it’s more dangerous or humiliating for Corbyn to be a leader, then he’s a leader. If it’s more dangerous or humiliating to be a follower, then he’s a follower. Sometimes he’s too racist, other times he’s not racist enough.

Bower flings shit at the wall and hopes it will stick. Even seemingly arbitrary or value-free details like where he grew up are reported with a sinister edge, to the point where you’d be forgiven for thinking that when Jeremy Corbyn goes for a piss, it’s because he wants to overthrow the urinal.

This is the way the hatchet job works, and in the hatchet job there is no room for nuance and little room for interest. The story has already been written before it is written. This is the way Bower has seemingly operated for a while now: identify a man at the heart of the news – Simon Cowell, Gordon Brown, Tony Blair, Bernie Ecclestone, among others – and then get a book out on them while it’s still likely to sell.

Dangerous Hero will continue to be welcomed by those eager for material to hammer Corbyn with, material that can be used to keep the partisan news cycle turning, grist for the content mill.

All of which doesn’t add up to a particularly coherent character portrait. Bower is an elderly baby boomer, and like a lot of men his age he’s most interested in telling you, at great length, why he is right. He appears to show absolutely no understanding of – and very little interest in – why Jeremy Corbyn became Labour leader and why some people – particularly young people – support him.

Of Labour’s 2017 general election campaign, which basically re-introduced the British public to traditional European social democracy, Bower writes that Corbyn was "appealing to the disgruntled: trade unionists, public service workers, students, the conscience-stricken and disappointed home-seekers – above all, to those aggrieved about their situation". He described this as "Adopting Hugo Chavez’s tactics". Elsewhere, Corbyn is found reaching out to "victims and losers" and his "ethnic constituents". He suggests MI5 pursue large-scale tax evasion, rather than go after welfare claimants, who Bower refers to as "feckless and fraudulent". Imagine, a Labour politician appealing to these people and thinking these things!

In a recent New Yorker article, the modern master of political biography, Robert Caro, wrote about the process of researching his multi-volume – and as yet unfinished – biography of the president Lyndon Johnson. At one point, Caro and his wife moved to the Texas hill country, where Johnson grew up, for three years, because the author felt as though this was the only way to understand his subject. There, Caro took Johnson’s brother to their childhood home and got him to recreate the family dinners they had as children.