OVER THE LAST 20 years or so Philip Roth has put on one of the more extraordinary late-season performances in U.S. literary history. No late bloomer, Roth from the very start of his career with Goodbye, Columbus, which nabbed the National Book Award in 1959, has won high critical acclaim; in 1969 his great comic novel Portnoy's Complaint was a sensational bestseller that vaulted him into wide popular renown.

But success didn't spoil Roth. On the contrary, it seemed to spur him on, as he proceeded into a high-voltage middle age with his series of Zuckerman novels (The Ghost Writer, Zuckerman Unbound, The Anatomy Lesson and The Counterlife) through the late 1970s and '80s.

In the course of his half-century-long career he has bagged every major literary prize except the Nobel, some of them two or three times. And since the early 1990s he seems not only to have accelerated the pace of his production but turned out a remarkable run of first-rate books. His memoir Patrimony and such knockout novels as Sabbath's Theater, I Married a Communist, The Human Stain and American Pastoral have been followed in the new millennium by a series of tight, intense, finely wrought novellas like The Dying Animal, Everyman and Exit Ghost.

It's not that he's necessarily gotten better with age but that he has sustained a consistent level of energy and amplitude of ambition that has made him for his generation what Saul Bellow was for the previous one: the dominant American novelist of his time.

Since the much-overrated counter-historical fantasy The Plot Against America in 2004 (which literate liberals vainly wished would somehow deconstruct the Bush regime), Roth has issued a string of short narratives, each under 200 pages, which continue his unflinching exploration of the ultimate theme, Death, culminating (for now) in his new book, The Humbling (Houghton Mifflin Harcourt, 2009, 140 pages, $22 hardback).

Once again here, as in his other recent efforts, Roth tackles some of the most unpleasant but inescapable realities of the human condition, mainly the implacable fact that the body tires and dies even as the spirit strives to survive, mourning its losses while desiring what it can't have: the passionate if passing physical vigor of youth.

As Portnoy proved, these passions, primarily sexual, can be a torment, but they infuse experience with a vital charge that fades for most of us as we age. Roth has raged against time's ravages for decades, but these late books (the author is now 76) take the fight to another level. If his writing is to be believed, Roth is angry at nothing less than Fate, humanity's primal doom, each person's personal death sentence. The heart of the matter is how one faces this inexorable truth. And his protagonists seldom do it with grace.

In The Humbling, Roth's antihero is an aging actor named Simon Axler, a star of the Broadway stage who now, in his mid-60s, finds himself unable to perform. In a version of stage fright, or what athletes call choking, Axler has frozen up in his latest plays and come to the conclusion that he's finished, that he has tarnished his reputation and blown his career, that his blazing earlier successes in the spotlights have turned to ash. He is depressed, to say the least, despairing at the loss of his mojo, charisma, genius, juice, whatever you call the life force of a performer.

Into this depression steps Pegeen Stapleford, the daughter of former colleagues, a hot young lesbian academic who decides to try out Axler as her lover. Whatever gyno- or homophobia Roth may be working out in The Humbling feminist critics will surely try to explain. What interests me is that the novelist has wrought another high-tension tale of a man past his peak who is trying to cope with his declining powers. The story is fat-free for all 140 pages of its grim but relentless telling, each sentence an essential step to the next, the narrative stripped of rhetorical excess, no time to waste on extraneous detail. The urgency of Roth's attack on the form mirrors that of his thematic obsessions. Like every moment in a fleeting life, every word must count.

The Humbling is strong and stark, from the beautiful jacket design by Milton Glaser to the dark dénouement of the final pages, and its vision is nothing if not bleak. It's hard to say whether Axler is a tragic or pathetic figure, a Shakespearean or Chekhovian hero, or just an absurd embodiment of life's arbitrary breaks. "Yes," the actor muses, "everything gruesome must be squarely faced." Roth the author meets this challenge with the steel nerves of a surgeon.

If you're looking for comfort or consolation, look elsewhere. Expect to be unsettled by this troubling book.

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