In the early evening of 12 November 2015, three cars left Charleroi in Belgium, arriving a few hours later at a rented house in the northern suburbs of Paris. The occupants of the cars – or “the death convoy”, as they called it – were Islamic State terrorists who, the following night, rampaged through the French capital. Three attacked the Stade de France, where a football friendly between France and Germany was being played. Arriving late, they were denied entry to the stadium and blew themselves up outside.

At the same time, another group opened fire on cafes and bars in the city centre. Two members fled, while another walked into a restaurant and detonated his suicide vest. Meanwhile, the remaining trio entered the Bataclan theatre, where a crowd of 1,500 were attending a gig by the US rock band Eagles of Death Metal. The attack and subsequent siege lasted two and a half hours and ended with all three terrorists dead. Across the city, 130 people had been murdered and hundreds more injured.

Five years later, in the autumn of 2020, on the eve of publishing his new book, Yoga, and reeling from a difficult few years – mental illness, divorce, legal battles – Emmanuel Carrère was hunting for a subject. The author, who wrote fiction before branching into true crime, unconventional biographies and a string of extraordinary, deeply exposing memoirs, making him one of France’s most highly regarded writers, contacted an editor at the news magazine Le Nouvel Obs putting himself forward for work – “You know the kind of stuff I’m comfortable with: less opinion pieces than fieldwork, maybe a criminal case.”

What the editors of Le Nouvel Obs eventually decided on wasn’t just any criminal case, but the largest in French history: the trial of those accused of involvement in the Paris terror attacks of 13 November 2015 (Friday, or vendredi, 13: V13). Everything about it was unprecedented: it would last nine months, with the plaintiffs’ testimony alone taking five weeks. There were 1,800 of those plaintiffs, a legal brief comprising 542 volumes which, if stacked, would stand 53 metres high; 20 defendants, and nearly 400 magistrates and lawyers, all occupying a 650sq metre, €7m (£5m) purpose-built courtroom at the Palais de Justice.

Carrère’s task was to show up, observe and file a weekly piece, and this book (translated from French by John Lambert) is the result. In 2009’s Other Lives But Mine, he managed to make the workings of a provincial small claims court compelling. The challenge posed by a trial as inherently dramatic as V13 isn’t how to render it interesting, but how to traverse its morass of detail and sometimes contradictory defence testimony. The skill with which he does so is extraordinary. In Carrère’s hands it becomes a lattice of absorbing storylines: will Salah Abdeslam, the sole surviving attacker, break his silence and take the stand? Why did Mohamed Abrini resign his role in the slaughter during the death convoy’s drive to Paris, then fail to blow himself up in an attack on Brussels airport four months later? What happened to Sonia, who tipped police off as to the location of Abdelhamid Abaaoud, the cell’s leader, several days after the attack? Will the three defendants not currently in custody, who need to be resident in Paris for the duration (one of them rents an old woman’s garden shed for €600 a month), be found guilty of criminal association with terrorists?

The first part of Carrère’s book, however, is devoted to the plaintiffs’ testimony, the majority of which comes from the Bataclan. It is hard to read these accounts of the terrible rhythm of death – “A shout a shot, a sob a shot, a ringtone a shot” – of people crawling through “human mud”, or of one of the attackers showering the pit with “a confetti of human flesh” when he blows himself up on stage. Carrère also relates the story of the 131st victim, a young man who killed himself two years after escaping the Bataclan. This ugly litany of violence makes for grim, queasy reading.

There are startling moments of human kindness and generosity, though, and Carrère is ever alive to striking details. The plaintiffs wear ribbons of green or red, which denote their willingness or otherwise to speak with journalists. Some, uncertain, wear both. When a plaintiff’s testimony is particularly good, the sound of clicking keyboards suddenly rises from the press benches (“Such a casting-call attitude is terrible,” Carrère acknowledges, “but how to escape it?”). Early in the proceedings, tipped off by a lawyer, the author slips into a small basement courtroom to briefly watch the trial of another terrorist, Carlos the Jackal, who has lodged a final appeal against the sentence handed down for his grenade attack on a Paris pharmacy in 1974.

As an account of what it was like to sit in the V13 courtroom, a “unique experience of horror, pity, proximity and presence”, Carrère’s book is absolutely gripping. But if there is an area in which it could, on its own terms, be said to fail, it is in the provision of answers. At one point, he reports “an astonishing sentence uttered by Abdeslam at the beginning of the trial and which, to my knowledge, went largely without comment: ‘Everything you say about us jihadists is like reading the last page of a book. What you should do is read the book from the start.’” This statement persists in Carrère’s mind as an encapsulation of what he expects from the trial. But while the terrorists framed their actions as a response to French involvement in Iraq and its bombing of Syria, there is a difference between a political cause and the willingness to do what these young men did (or, in Abrini’s case, didn’t do).

In the end justice is done, sentences are handed down, and at least some of the plaintiffs and the families of victims find closure. Yet despite Carrère’s attempt to imagine his way into the hash smoke-filled space of Les Béguines, the Molenbeek cafe where the attackers congregated to watch grisly IS videos of beheadings and burnings on Brahim Abdeslam’s laptop (and, the defendants claim, videos of IS building schools in Raqqa), he cannot penetrate them, or the fatal decisions they made, to any real depth.

The problem is perhaps one of form: a weekly magazine column isn’t an ideal medium for deep insight, and even if these pieces have been edited, shaped and expanded for the book, this is still fundamentally a collection of reports (as betrayed by the frequent repetitions – necessary in a weekly format, irritating here). There is also the matter of the raw material. Carrère may disagree with Manuel Valls, prime minister of France at the time of the attacks, who said that to try to understand the terrorists’ actions was to justify them. But while he imagined their testimony would be captivating, it turns out instead to be a “poor mystery: an abysmal void wrapped in lies, which one regrets with stunned amazement having spent so much time thinking about at all”.