In October 1894 Captain Alfred Dreyfus was arrested on the charge of high treason, accused on derisory evidence of revealing French military secrets to the Germany embassy. There was indeed a spy within the ranks, but the military authorities chose Dreyfus as the culprit, pretty much because he suited their purposes. He was Jewish, he was wealthy, his manner was withdrawn, taciturn, all suspiciously unFrench attributes. After the catastrophic defeat by Germany in 1870, the French army was on the defensive, national pride in shreds; French Catholic antisemitism was vocal, and on the rise. At his court martial, the army provided the military judges with secret and doctored evidence. On this basis, Dreyfus was condemned to life imprisonment on Devil's Island. He spent four years in horrific solitary confinement there, oblivious to the forces that rose up in France to defend him as evidence gradually emerged of further army forgeries and machinations, and the affair turned into a scandal which tore apart French political and social life for more than a decade.

The Dreyfus affair took on mythic proportions immediately; more than a century after the revolution, traditional France (anti-Dreyfusards) and Republican France (Dreyfusards) faced each other again across the barricades. This is an overgeneralisation, but a useful one because so much has been written about the Dreyfus affair.

The reasons for this are simple: the story itself is fascinating, better than the very best Conan Doyle or Dickens could do. It is also a great political conspiracy in which army, church and state perpetrated a gross injustice and then attempted to cover it up. At the core of the affair is the basic human longing for justice, and the fear of every citizen that the authorities who control our lives will withhold it from us. With the final exoneration of Dreyfus in 1906, justice triumphed: the triumph of Everyman.

Today the Dreyfus affair is still constantly evoked: in connection with the death of David Kelly, Guantánamo and the Iraq war. The Dreyfus affair led directly to the separation of church and state in France in 1905. Today the French insistence on their secular state and thus the prohibition on the wearing of the veil or burqa is misunderstood by those (often British) who insist on failing to understand how French civic principles developed after the Dreyfus affair. The similarities between the way the Catholic hierarchy handled the affair, and the virulent antisemitism of certain Catholic orders at the time, with the church's handling of sex abuse scandals today, are both obvious and shocking.

This is a perfect time for a new look at the case. We live in the shadow of monstrous events – illegal invasions and wars, financial crashes, tribal genocide and paedophile priests – and the Dreyfus case was never merely French: it became an international cause célèbre and a symbolic blueprint for any seemingly hopeless fight in defence of justice and the rule of law.

By 1905, several hundred books and pamphlets had been published about the case. Over a century later the number is in the thousands. What can historian Ruth Harris, of New College Oxford, add to our knowledge and understanding? Her title is misleading in that the book is not about Dreyfus himself – "The Man on Devil's Island" – but a most comprehensive and nuanced account of the participants on both sides of the imbroglio. Harris's claim to provide a reassessment of the case by interweaving knowledge of the finer points of the "mixed motives" of its protagonists with incisive understanding of the complex influences at play in fin-de-siècle Europe, is beside the point. The fact is that every writer on the subject brings an individual "passionate involvement" and insight to any reconsideration of this mythic tale, and what marks Harris's contribution is her formidable research skills, her exceptionally wide general and historical reading, and her always interesting eye for the revealing anecdote or pen portrait.

Dreyfusard belief in "Catholic priests who screw chickens and goats" jostles with anti-Dreyfusard accounts of Jews collecting Christian blood "in a shallow metal bowl to make matzos". Bizet's widow, a Dreyfusard, pursued by the eccentric pianist and composer, Delaborde, "who travelled with two apes and more than a hundred cockatoos" and the mad anti-Dreyfusard neuroanatomist Jules Soury, who inhaled "dried tubercular spittle to hasten his own death", give the tenor of Harris's lightness of touch. Even better is the scope of her investigation: the book is rich with information about ranting Assumptionists and devious Jesuits, delirious Catholic antisemites, demonised Jews, hypnotism, graphology, spiritualists, mediums, intellectuals, artists, politicians and fabulous salonnières and women of the world.

Zola described the Dreyfus affair best: "It is gripping . . . it is exciting! It is horrible! But how it is great at the same time." Harris requires no claim to originality to prove that she is a first-rate narrative historian, well suited to report a rare historical event which illuminated all individual infamy, all individual heroism. Her book is certain to be one of the many essential texts on this timeless saga.

Carmen Callil's Bad Faith: A Forgotten History of Family and Fatherland is published by Vintage.