France's Socialist President François Hollande hoped he could keep his love life private and distinguish himself from his showy predecessor Nicolas Sarkozy. But his feisty first lady appears to have dashed those plans.

• Royal anger over 'face to slap' headline (30 Dec 11)
• Are politicians' secrets no longer safe in France? (10 Nov 11)
• Former partner Royal backs Hollande (12 Oct 11)

Valérie Trierweiler has been quiet since launching an explosive tweet in June that rocked French politics and made headlines across the world, but her alleged feud with the president's ex-partner – the mother of his four children – continues to fascinate.

"The Battle of the Ladies," said the front-page headline of the latest edition of Le Nouvel Observateur magazine, beside a picture of Trierweiler and Segolène Royal, Hollande's former partner of three decades.

"The Royal Headache," Le Parisien punned last Friday, while the weekly Marianne led with: "Secrets of a Trio from Hell".

The continued interest has been fanned by the publication of three books over the past month – with more scheduled before year-end – that lay bare what their authors claim to be the tumultuous relations among the trio.

The most virulent, "La Favorite", by Laurent Geilsamer, a former journalist at Le Monde newspaper, directly addresses Trierweiler, a twice-divorced 47-year-old journalist and mother of three.

"You have shown yourself to be unconventional, imperial, amorous, explosive, unpredictable. And clearly dangerous," he wrote of the glamorous woman who has not married Hollande and who is keeping on her job at Paris Match magazine.

"L'Ex", by Sylvain Courage, traces the triangle back to the 1980s, when Hollande was already with Royal, a fellow Socialist politician, but, according to the author, was also enamoured of Trierweiler, then a young political reporter.

It follows their relations over the next couple of decades, during which Hollande and Royal – who are now both 58 – moved up the ranks of the Socialist party and had a family.

The former became party chief and then got elected president, while Royal made a failed bid to run for the presidency in 2007 against Sarkozy.

During that time Trierweiler rose up the career ladder too, hosting television shows and writing political articles for Paris Match.

Their intertwining worlds meant that contact was frequent, but it was reportedly not until 2005 that Hollande finally began a romantic relationship with Trierweiler.

That did not prevent him from publicly pretending to still be with Royal as she battled Sarkozy for the presidency in 2007, a pretence aided by France's compliant media which largely regarded politicians' private lives as off limits.

When Hollande made his own bid for the presidency this year, he appeared to have achieved harmony between his past and his current lover. The two women were pictured shaking hands at a party conference, and Royal publicly backed her ex.

Hollande presented himself to the French as "Mr Normal" to distinguish himself from Sarkozy, whose tumultuous private life – which included a divorce just months after taking power followed quickly by marriage to a supermodel – dismayed many voters.

But those hopes were dashed in June when, with a single tweet, Trierweiler managed to take a swipe at Royal, put herself publicly at odds with Hollande, and throw a spanner in the works of the Socialist party.

The Twitter post appeared to be an innocent message wishing a politician good luck in his bid to win a parliamentary seat in an upcoming election.

But it was obvious that the real target was Royal, who was standing against the dissident Socialist candidate Trierweiler had wished good luck – and who went on to defeat her.

That tweet sparked frenzied media coverage in France and for many confirmed that the independent-minded first lady had not put aside her rivalry and was going to be a problem for the new president.

"Hollande has asked her to choose between her career and representing France, so she is suddenly reduced to minimum service and she's not very happy about that," Courage, the author of "L'Ex", told AFP.

And Royal is not happy either, he said, pointing to an interview she gave this week saying she had been the victim of an "injustice" in the June election.

"She's waiting for a gesture from the president, who is embarrassed because obviously any gesture will be interpreted as favouritism," said Courage, adding that Hollande's hopes of being a "normal" president are a mirage.

"His private life has blown up in his face. It was a brutal and troubling return of these questions to the top of the news agenda," he said.