If there's a better novelist than Ian McEwan writing in English today, it's hard to say who it might be. The British writer possesses not just storytelling ability, but also a knack for narrative drive that pulls readers through his works. He can write exquisite love scenes, and his virtuoso set pieces -- the bloody shambles of the Dunkirk retreat, a busy neurosurgeon on his rounds -- transform masses of research into supple, absorbing prose. McEwan's last book, Atonement(2001), which somehow escaped winning the Man Booker Prize, pulled all his gifts together in a flat-out masterpiece. His new work, Saturday -- shorter, more tightly focused and deeply political -- picks up where it left off.

McEwan's primary technique is to structure his novels around a flash moment that shatters the stability and assumptions of his characters -- the abduction of a three-year-old girl(The Child in Time), a freak fatal accident(Enduring Love)-- and then chronicling the raw emotions that are unleashed. It's no surprise that 9/11 haunts McEwan -- he wrote a famous Guardian column about it four days after the terrorist attacks -- and no surprise that it haunts the first novel he's written since.

It's Saturday, Feb. 15, 2003, the day perhaps two million people took to the streets of London to protest the looming invasion of Iraq. Henry Perowne, eminent neurosurgeon and happy family man, is trying to make his way about the increasingly gridlocked city(shades of Leopold Bloom criss-crossing Dublin in Ulysses, the original day-in-the-life novel). Taking a shortcut across a closed-off road, Perowne causes a minor car accident and gets into a confrontation with a violent young man named Baxter. Later that night, during a Perowne family reunion, Baxter invades the surgeon's home, threatening everything Perowne cares for.

Echoes of the debate over the Iraq war are obvious, and the readers' response to Saturday may well fracture along political lines. A surface reading will take it as a pro-war novel. Perowne, the protagonist, is an invader himself, albeit a beneficent one, who cuts into patients' brains, risking their existence in order to save them. And he encounters a madman, the roots of whose madness he -- among only a handful of experts -- can diagnose and ameliorate, if not cure; the consequences of leaving madness unchecked is one of the novel's major themes.

But a closer look shows McEwan is not so simple-minded as that. Saturday is far from being an unusually well-written propaganda sheet for either side. Perowne can neither shake his ambivalence about the invasion nor dismiss it from his mind. How can he, with a pair of resolutely anti-war children and recurring memories of a badly scarred Iraqi patient who sardonically calls the giant demonstration a march for "peace and torture?" In much the same way so many others did two years ago, Perowne tends to the pro-war position when he argues with doves, and to the anti-war side when he meets a hawk. Significantly, the action that brings on the Perowne family's 9/11 -- the car accident -- is the surgeon's own doing. And his eventual response to Baxter is both surprising and understandable.

McEwan has always complemented his more traditional writerly talents with a post-modern awareness that his stories are made up, self-conscious inventions shaped in a search for understanding. Here he makes a successful incision into the mind of a brain surgeon, a character who -- despite his many virtues -- doesn't "get" fiction, especially novels that go on and on about the details of someone's life. In that sense, McEwan mercilessly mocks his own protagonist simply by making him so fully formed. But Perowne's blind spot is less an author's little joke than a plea for the saving grace of literature.

Cruelty, McEwan wrote in his 9/11 essay, is "a failure of imagination." Art, Saturday implicitly argues, offers the surest road into the minds of others. And also the strongest connection between minds, however damaged -- the novel's crucial scene turns on a remembered Matthew Arnold poem. Full of urgent questions and less than obvious answers, Saturday is vintage McEwan.