There is a saying in France: l’information s’arrête à la porte de la chambre à coucher – information stops at the bedroom door.

It was, until the advent of paparazzi and social media, THE golden rule of privacy for French journalists; a self-censorship that enabled former president François Mitterrand to maintain a second family – largely at taxpayers’ expense – with the knowledge of the press but not the voting, paying public.

Valérie Trierweiler’s score-settling book about her life with François Hollande, published this week, does not stop at the presidential bedroom door. It does not even knock politely, but kicks it off its hinges, trampling taboos, totems, rules and privacy in its muckraking wake. Merci pour ce Moment (Thanks for the Moment) has no racy sex scenes, unless readers find the image of a besuited Hollande kneeling on a bed with his head in his hands a turn-on, but is still a torrid read, described by one French commentator as “sentimental pornography”. It is also deeply disturbing on many levels.

Benignly billed as a “memoir”, it leaves a sense of grubby prurience, of things one would wish to but can never un-know and a bitter aftertaste. It is also on its knees, page after page, begging the question why?

Why would an intelligent, sophisticated woman, and a former political journalist to boot, write a book that causes random harm to so many, including the author, and does such a great disservice to women? Why become the living, breathing embodiment of the sexist old adage about hell and a scorned woman’s fury? Why gain a certain sympathy, following Hollande’s shabby secret visits to his lover (his scooter helmet on head, bag of croissants on order) and even shabbier 15-word public statement “putting an end to their shared life”, but then exchange this compassion for a nation’s antipathy and opprobrium?

Most women and men have said and done things to their partners that they would not wish broadcast to the wider world. Why would anyone choose to make their jealous rages public in all their ghastly, intimate detail? Even in the most agonising throes of bitterness, jealousy, vengefulness, humiliation and heartbreak – and Trierweiler has clearly suffered– is it right that she put her own woes above the general good? By targeting the unfaithful love rat of a man, the dignity of the presidency has suffered collateral damage.

To profess to being leftwing but to question Hollande’s socialist credentials by claiming, in one of the less credible passages in the book, that he “doesn’t like the poor”, damages by extension the socialist government and the French left at a time when they are already battered and facing a parliamentary vote of confidence. Even if Hollande deserved both barrels, did France? Was it, unlikely as it seems, for the money, a fat cheque for more than €500,000?

Trierweiler’s explanation is deeply inadequate. She bemoans the lies written about her and media intrusions into her private life that, she says, created a false image of “a woman who had my name, my face, but that I didn’t know”. Her surprise that journalists have picked only the juicy negative bits of the book is scarcely believable coming from a former reporter.

One answer lies in the image of Trierweiler that emerges from her own account: a fragile, insecure and hyper-jealous woman whose shaky confidence is shattered by the permanent presence of Hollande’s successful ex – the government minister Ségolène Royal – in the wings. Hollande is portrayed as cold and uncaring, though it has to be said he did have other things on his mind – apart from a mistress – including running France.

Two intimate scenes, among many, illustrate her solipsism. In one, Hollande has just been informed he is the new president and in the excitement of the moment rebuffs her suggestion about photographs. Unable to realise that this historic moment is not all about her, she flees to the bathroom and collapses on the floor. In the second, she complains that in between meeting Angela Merkel and travelling to Brussels for a summit, they have had no time to kiss and make up after a row, so she writes a long letter for him to read before he meets world leaders.

The real answer behind this sorry tale could be that Trierweiler could not deal with the demeaning role of presidential PR prop and public property that the role of Premiere Dame, or any kind of political wife now involves. Nor could she suffer in silence the humiliation of being pushed out of it. Whatever her motives it is hard to believe Trierweiler failed to foresee that the fallout from her disclosures would be nuclear.

And if she was looking for sympathy, she calamitously misjudged the public mood. Ironically, she has unified France’s truculent political factions. Even Marine Le Pen, leader of the far-right Front National, declared it a dishonour on the country. And while it has made the French president look ridiculous, it may help his catastrophic popularity ratings. Leading commentator Renaud Dély wrote inthe left-leaning magazine Le Nouvel Observateur that the French might consider Hollande a “bad president”, but that Trierweiler’s “repugnant” work was an attack on democracy. “To maintain a semblance of dignity in the public debate, citizens must reclaim the right not to know what happens in the president’s bedroom. By dragging us there, with a detour via the Elysée bathroom, Valérie Trierwieler has attacked that right,” Dély wrote.

You don’t have to go that far to see this as an indiscreet and undignified tale that should not have been told – at least not while Hollande is running France.

• The standfirst of this article was amended on 8 September.