Rosa Prince, the online political editor for the Telegraph, was an interesting choice for Jeremy Corbyn’s biographer, and when I say “interesting”, of course I mean “perverse”. It is a bit like asking Owen Jones to write a biography of David Cameron: no one would doubt his gusto, but there would be the wrong circle, wrong age, wrong hinterland, no friends of friends of aunts of friends and, crucially, Cameron’s associates would be immensely suspicious of Jones, as Corbyn’s are of Prince. It would avert the danger of a hagiography, but at the cost of any close-quartered insights. All the reminiscence is hacked from articles that have already been published, mostly in the Daily Mail. Prince pores over an incident when Diane Abbott, then Corbyn’s girlfriend, was sighted by friends in his bed, wrapped in a sheet. It’s not a new story though it appears to be a new account, its prurient inclusion justified on the Laura Kuenssberg defence (“I’m a journalist, and I found out a thing”).

It’s frustrating; because the thing about socialism, as the saying goes, is that it takes a lot of evenings, and nobody spent more evenings on it than Corbyn. There are hundreds of people: ex-flatmates, friends on the board of the Jackson’s Lane Community Centre, comrades at Tony Benn’s soirees, who don’t just remember him intimately, but have funny stories. Meetings of gnarly Greens and assorted progressives, just after Corbyn’s election as leader, were like a cheerful wake after a good innings (“Do you remember the time he made you drive that terrorist to Dungeness?” “That wasn’t a terrorist! That was a vegetarian”).

In testament, I suppose, to the loyalty the politician commands, almost none of those voices – bar Tariq Ali, in the most head-down-and-behave tones – appear. In their stead are people who knew Corbyn very distantly, before they went on their own political journey to the right: Leo McKinstry, a thunderer on the Daily Express, the wonderful Telegraph doctor-columnist James le Fanu, who was anything but embedded with the socialist left. From these remote associates, Prince elicits reminiscences of terrifying blandness, such as this, from le Fanu, “‘[His flat] was an absolute tip,’ he says. ‘Not stylish. There was quite a lot of coming and going.’”

Not so damaging to the pace, but perhaps worse for the credibility, the author has a total and determined lack of interest in the ideas of the left. She takes us on Corbyn’s tour from Jamaica to Latin America to north London, never mentioning or apparently noticing the major leftwing landmarks – post-colonialism, the roots of buen vivir, the Kilburn manifesto – instead confining herself to the broadest possible understanding of leftwing ideas: “What Corbyn saw of the inequality in Jamaica and Latin America seems to have left an indelible impression. He returned radicalised, and for the rest of his life would be on the far left of British politics.” This tells when the author tries to explain what forged Corbyn’s socialism in the first place: if your understanding of the left is simply that it takes stuff away from people with a lot, and gives it to people with nothing, then you would indeed find it confusing that anyone with more than nothing would espouse it. “Wikipedia told me that Newport was a Britain in Bloom finalist. It seemed an incongruous place for a people’s revolutionary to have spent his formative years.” Everybody middle class makes a “highly unlikely socialist”. Corbyn’s father’s attempt to learn Russian was “an unlikely interest, given that this was the height of the cold war”.

Prince describes Corbyn’s childhood home with the onanistic admiration of an estate agent, “wooden beams, generously sized rooms extending off into yet more rooms; a large, open kitchen with a utility area and sculleries; living rooms, reception rooms, dens”, concluding, “what an extraordinary journey Labour’s new leader has gone on.” I finished it feeling quite protective, not of socialism but of the middle classes, that anyone would think this prissy, curtain-twitching, self-interested anti-intellectualism would describe the limits of its political identity. But as a portrait of a man it suffers, too: Corbyn’s is a life lived through ideas. However ridiculous you judge them, you need to know what they are. Otherwise, in their place, you get information like this: “Corbyn and Chapman [his first wife] moved a few minutes’ walk away to a one-bedroom, ground-floor flat on Lausanne Road, one of a series of streets running in straight lines between two major thoroughfares, the A105 and the B138, giving them the nickname ‘The Ladder’.”

This aversion to leftwing politics shows itself thereafter in a spirited refusal to distinguish between one cause and another – apartheid, Yarl’s Wood, ex-Guantánamo detainee Shaker Aamer, Syria, arms deals and privatisation. At one point, Prince refers to Corbyn’s objection to the CSA without saying what that objection was (to fathers being chased for money? To mothers not getting the money fast enough?) It seems like these distinctions might matter – luckily you can check in Hansard. The implication is of it all being just one amorphous leftie humus. There is no engagement with the idea that some people, maybe quite a few of us, think the politician who set up Yarl’s Wood for the incarceration of desperate people who didn’t have anywhere to run might have been a good deal crazier than the politician who went on a march against it.

Where Prince does engage is on the two hotspots of Corbyn’s past – Palestine and Northern Ireland. Her reporting here is competent and interesting, and she attempts, especially in the case of Corbyn’s association with Gerry Adams and Martin McGuinness, to put his side. Yet when all his critics are talking to her directly, and she is having to cobble his case together from cuts and the telly, it’s like drinking his arguments through a veil. Having said that, the author seems satisfied that she is not describing a violent man, and is not about to amp up his past to make him look more bellicose than he is. It is pretty well impossible to spend your life on the side of the underdog and not end up having shaken hands with people who at least advocate blowing things up, just as it is well-nigh impossible to spend your life on the side of authority and not end up having sold arms to dictators. These are things that only bloggers and the Daily Mail pretend not to understand, and she didn’t fall into that trap.

When the Labour leadership campaign begins, the book ignites; partly because the author’s contacts suddenly come in useful. There are some wonderful minute-by-minute accounts of Andy Burnham and Liz Kendall’s campaign teams, drinking Limoncello in Pizza Express (yes, really), wondering what on earth to do. The fact that we all know the outcome, of course, gives it the extra piquancy of re-watching Towering Inferno.

Her acceptance of the “centrist” Labour account still has an outsider’s lack of critical distance. It has become fashionable to recast the 1990s and 00s as a period when “some of us spent decades fighting the hard left” (in the account of Paul Richards, a former special adviser to Hazel Blears); while Blair was doing the heavy lifting of wooing normal people, warm bodies on the ground were doing the painstaking work of rooting out Trots like headlice. It just isn’t how I remember it, I’m afraid: rather, a process as slow as the cooling of a bath, in which some left over Blair’s removal of Clause Four, which ended the party’s commitment to mass nationalisation; some over unilateral disarmament; some over Blair himself; many over the Iraq war; a lot of people left and still came to the pub after meetings, or didn’t technically leave but stopped turning up. The CLP went bald, basically, and that’s what got rid of the head lice; then when the regrowth started, the head lice came back. Obviously, I could be wrong. I’m only describing one constituency; all the others might have been locked in a bare-knuckle fight between realists and radicals. But a bit more range and bit less credulity might have helped.

I’d enjoy a parody Twitter account in which Prince would take her meticulously uninterested, slightly spiteful analysis to all the figures of the left and beyond – “Marx (who at this point was wearing shoes with genuine leather uppers)”; “Gramsci (whose waist clearly pointed to a man familiar with pricey carbohydrates, such as pasta)”; “Lovelock (whose house, being at the end of the A303, clearly shared none of his concerns about fossil fuels, which cars use)”. But I wouldn’t run it to this kind of length.

• Comrade Corbyn by Rosa Prince (Biteback, £20). To order a copy for £16, go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.