A red-haired woman drifts through these pages like a leitmotif.

This is a reminder the young James Ellroy once wished his mother dead, and had that wish come true in one of the most celebrated murders of the last century. He has remained trapped in that 1940s pretty much ever since, and for all the virtuosic mix of fact and fiction, invented characters and real, in this epic condensation of the extraordinary cultural and psychic conflicts that erupted either side of Pearl Harbour, Ellroy's world remains personal. It is operatic rather than realistic, minimalist in the sense of a now canonical strain of American music that obsessively reprises its own basic material, and ultimately turns it maximal.

This is Ellroy's largest novel to date, and seems to mark the beginning of a new phase in his writing career, a second "LA Quartet". Long since graduated from the 'crime writing' genre, he now works a field pegged out by Nathanael West, Norman Mailer, Hubert Selby Jr, Thomas Pynchon and Don DeLillo, a kind of encyclopaedic satire that lies down all too comfortably with the horrors it depicts, indulges vice to condemn vice. It is the most uncomfortable but also one of the most courageous literary endeavours of recent times. Ellroy famously declines to have much truck with the modern world. He inhabits a pre-digital age in which human communication is blatantly, blaringly direct and visceral. It is worth a look at how often contemporary scriptwriters and directors resort to cellphone calls and e-mails to tell a story. Ellroy's characters communicate by fist, lead sap, handgun, shotgun, in ritualistically formalised violence of one kind and another, and in a language that is as elaborate in its idiolects as Dickens's great Victorian urbanscapes.

When he blends fictional characters with real people - Joe and Jack Kennedy, Barbara Stanwyck, Salvador Dali, Bugsy Siegel - he plays with the very notion of real and invented, for aren't all of these characters in some way inventions, and don't his principals seem a little more true to life as a result?

The background to Perfidia is the treatment of Japanese-Americans at the time of America's entry into the war. This in turn sets loose a whole stew of cultural and ethnic hatreds and interdependencies: Chinese versus Japanese; Protestant Irish versus Catholic Irish; Catholic Irish against British; Italians and Hispanics opportunistically occupying any momentary vacuum; Reds at war with capital; Nazis and Jews, contra mundum. The book's central characters are a whisky-priest policeman called William H Parker, a brilliant Japanese-American police chemist called Hideo Ashida, the fiercely intelligent but destructive Kay Lake, and the ex-IRA man Dudley Smith, for whom the impending war is rich with possibility.

What brings them together, specifically and in addition to the atmosphere of pervading nationalist paranoia, is the apparently ritual suicide of a Japanese family, on the very eve of the bombing attack on Hawaii.

It becomes clear, in a nicely noirish unfolding, that the true verdict is not seppuku but murder. Cue a process of investigation that parades a familiar-looking gallery of suspects who are clearly not perpetrators but are nonetheless profoundly complicit in what leads to the killing. The narrative has a sleepless, hopped-up quality, with Benzedrine a useful narrative device that keeps events moving, and moving fast, for each of the 24 hours of each of the days that the book straddles. There is some sex, mostly done in fastidious cutaway, like a 1940s movie. There is a good deal more violence, and an unflinching fixation on its aftermaths. There is, almost literally, nowhere to go for 700 pages.

So what, apart from an apparent desire to dwell on unpleasantness, is all this about? Perfidia is a crime novel, but mainly in the sense that it investigates in a deeper way than before the ultimate crime of war, and the meta-crime that is society itself. Ellroy rages - and there is no one who can rage quite like him - when he is described as a 'nihilistic' writer. He is justified in his anger, for the description depends on a profound misreading of his work.

At its heart is what he has described as the "civil contract", the pattern of dependencies, hostilities, needs, addictions, residual or evangelical faiths, science, superstition and downright cussedness that holds us together. Or, critically, that held us together in the era that Ellroy obsessively inhabits. It is the subsequent breaking of that civil contract that is his great theme, and in this he differs strikingly from the Don DeLillo of Libra (an acknowledged influence) in which the fractured language is a symbol of precisely that, a society fractured with anomie and existential uncertainty. Ellroy believes, as Mailer was inclined to believe (and was laughed or spat at for it), that violence represents some kind of desperate reaching out, part of the fearful bond that holds together a country like America that is mongrel and alien to its very roots.

Perfidia is a brave and moral book. It is not a beautiful book. Its defining characteristic is honesty, its engine principle, qualities that are vanishingly rare in contemporary fiction. It may be set in the 1940s, at a very specific and not so very distant moment in historical time, but its real subject is now.