Deborah Levy argues that Don DeLillo's great atomic epic pushes the limits of the novel to breaking-point and beyond
Don DeLillo is now in his early sixties and has written 11 novels. I keep two of his earlier books, White Noise and Mao II, on the bookshelf that contains the work of authors I need to re-read every so often. These include William Blake, Walt Whitman and J G Ballard. What these writers share with DeLillo is their intimate understanding of the inner life of their culture.

When White Noise was published in 1984, it offered the reader a new poetics to describe postmodern life. Often described as an apocalyptic novel it is, at heart, a celebration of the heroism of ordinary people and the small rituals they make from the panic of the everyday.

In Mao II, DeLillo continued his exploration of how cultural icons perform the roles that have been staged for them. If you look long enough at photographs of Mao Zedong and Andy Warhol, you will see an eerie similarity in their facial expressions. Mao II juxtaposes these two icons from East and West to articulate the novel's themes of emptiness and fullness. It is also an autopsy on the role of the writer.

The novel's anti-hero, Bill Gray, is a failed novelist who finds refuge in literal, rather than literary terrorism: "Bill was not an autobiographical novelist. You could not glean the makings of a life-shape by searching his words for clues. His sap and marrow, his soul's sharp argument might be slapped across a random page, sentence by sentence, but nowhere a word of his beginnings or places he has lived in or what kind of a man his father might have been."

Underworld (Picador, pounds 18), DeLillo's new novel, circles exactly these autobiographical concerns. The book is dedicated to the memory of his mother and father and is, in many ways, an excavation of his own background as an Italian-American. It is all the more poignant that Underworld recalls the Bronx of the 1950s, as seen through the eyes of a first-generation American.

Perhaps it is because DeLillo had access to ways of seeing and being that were not American that he can so acutely decode the culture, both as an insider and outsider.

The novel opens in 1951, when two streetwise Bronx boys try to scam their way into a legendary baseball game played in New York. The famous home run that won the game was described at the time as "The Shot Heard Round The World". It probably wasn't heard in the former Soviet Union, however, because the country was busy testing an atomic bomb.

DeLillo uses these two major public events to frame the key movements and moments in the 20th century. Themes as diverse as Vietnam, infidelity, cultural identity, fame, miracles, the World Wide Web, Lenny Bruce and his wired deconstruction of the American soul - all get the DeLillo workover.

Take the Cold War which, he suggests, was a useful psychic boundary: "you could measure hope and you could measure destruction". When a character from the Bronx travels through Eastern Europe in the days when the Iron Curtain was well and truly drawn, he notes that his "bowel movements" begin to reek. He is shamed, appalled. It is as if he has internalised the Cold War, literally, in the lining of his guts. When he defecates, "the smell that surrounded him was infused with geopolitics".

But it is "lonely-chrome" America that DeLillo writes about best: kids who eat "Hydrox" cookies "because the name sounded like rocket fuel", graffitti that tell a story of backstreet life in one "tag", motels with sagging porches. The most enthralling chapter, "Long Tall Sally", describes the novel's main protagonist, Nick Shay, driving into the desert to meet up with his ex-lover Klara Sax. He is apprehensive that he might appear to her as "a figure from an anxious dream come walking and talking across a wilderness to find her".

She is an artist who is working on a mass sculpture with a team of volunteers, stripping and re-painting hundreds of deactivated long-range bombers. DeLillo, as ever, is intrigued by the theatre of mass spectacle, whether it be war planes or crowds in stadiums. He suggests that even the most nightmarish events in the 20th century provide us with images that we make our own - as if they were snapshots in our own family album.

Klara Sax is a woman with a project. It makes her sexy (she is 72 years old), which is what characters compelled to act on the impulses that give their lives meaning often are. DeLillo calls it a "zone of exalted play". Shay's first glimpse of her after all these years is as a famous woman being interviewed by a French TV crew. Klara insists to them that her work is an art project and not a peace project - a kind of landscape painting that uses the desert itself as its frame.

DeLillo's writerly landscape has always effortlessly collapsed the apocalyptic with the domestic - especially children, and their highly-developed capacity for magical thinking. If Klara Sax re-imagines B52s, Nick Shay's son imagines he can make aeroplanes explode in the air just by looking at them.

And then there are Underworld's real explosions: the detonating of nuclear waste, the fall-out from marital betrayals with their explosions of tears and rage; fragmented cultural identities that find some cohesion in the exultation of the crowd.

DeLillo is a writer at ease with his medium. In Underworld, his language becomes so supple and kinetic that the experience of reading his prose sometimes resembles watching a film in which you want to see every twitch on the muscles of an actor's face.

I am not convinced that this is his best novel, however. Underworld is a fiction of fragments, essays, multiple narratives, but its centre seems to have liquefied. Is it possible to write about the connectedness of everything and anything, and not lose the edge of being partial? DeLillo has proved that it is possible, but not without some losses. The prose in places feels too leisurely, the pace and spin of its content too mellow.

It takes a great writer and a great book to provoke some troubling questions about contemporary fiction. Klara Sax's fictional project is rather like that of the conceptual artist Christo, who covered the entire Reichstag in plastic. Does Christo's image say more about the 20th century than the 800 pages of this novel?

In my view, Underworld is the masterwork that critics in the US have been quick to claim it as, but not for the same reasons. It is a masterwork because it takes a master to almost write himself out of a form. DeLillo is right to dare the novel to be the container, the vessel for his de- centred journey. For this reason, Underworld is a magnificent addition to DeLillo's awesome canon.