Hello, cruel world

A Long Way Down
By Nick Hornby
Riverhead, 335 pp., $24.95

The trick to living, as Vladimir or Estragon would tell you, is being able to tolerate it on the off days. Otherwise you wind up pulling a Hamlet with no third act of your own; you wind up, like the ragtag cast of ''A Long Way Down," standing on the rooftop of a North London tower block, ready to go over. Of course, if your planning is unoriginal, and you pick a popular spot to end it all on New Year's Eve (a popular holiday), you might encounter a bit of a queue: You can find yourself, as does one of the four existential vagabonds on Nick Hornby's ledge, ''in the process of turning a solemn and private moment into a farce with a cast of thousands."

The premise of ''A Long Way Down" -- a mordant, brilliant novel about four suicide if-onlys -- may startle some people and offend others; those will be the ones, though, who haven't discovered the tool of laughing at the black beast of despair. British author of the acclaimed ''High Fidelity" and ''How to Be Good," Hornby has long since proven his hilarity; what this novel confirms is the depth and generosity of his grasp of the tragic. Because it employs as a strategy a sort of game of human bumper cars, with its characters hurling themselves into one another's paths of pain and sorrow, the novel is full of emotional fender benders: Its piercing truths and tasteless pratfalls are meant to hold the unbearable sorrow at its center. It is a fiercely constructed story that unfolds entirely in the alternating voices of its four protagonists; in this regard, it calls to mind Graham Swift's ''Last Orders."

Not an ounce of excess or wasted effort is anywhere in sight. ''A Long Way Down" ought to be required reading for writing students who want to know how to evoke one set of circumstances with its opposite -- how to capture unspeakable pain with humor, how to suggest camaraderie with trenchant, piss-all irony, how to turn a novel based on suicide into a cello suite about how to go on living.

On the New Year's Eve in question, Martin Sharp -- former TV talk-show host, ex-con, seducer of 15-year-old girls -- is the first would-be jumper to get to the roof of Toppers' House. As he ruminates on his past in what he believes are his last moments, the memories aren't pretty: lost job, public drunkenness, divorce, alienated daughters, jail time, front page of the tabloids with the headline ''SLEAZEBAG" -- all because poor Martin, middle-aged bloke, had a moment of weakness and fell for a teenager. A timid woman taps him on the shoulder to see how long he'll be at the ledge; she's got it all planned out, see, and wants to get on with her schedule. This endearing soldier is a mother named Maureen, who hired nurses for her severely disabled son before she turned the key and set out on her last journey. Together, she and Martin stop an 18-year-old foulmouthed girl with a broken heart from taking the plunge -- she's still young, they tell Jess, and still deserves her chance at screwing it all up.

And then the pizza guy arrives: JJ, an American rock 'n' roller whose band broke up around the same time his girlfriend left him, has been reduced to delivering pepperoni, and on a run to Toppers' House decides he's had enough. By the time he gets to the roof, though, the three ahead of him have already foiled one another's plans, so that what started out as the world's loneliest moment becomes an impromptu group therapy session. Next to the troubles of his three compatriots -- even in the intolerably brattish Jess, the anguish is apparent -- JJ is embarrassed, so he tells them he's dying. His affliction, which he invents on the spot, is called CCR, an acronym he borrows from Creedence Clearwater Revival.

Thus begins an affiliation among four disparate and utterly inharmonious members of the human race, whose chief purpose, now that they have all this free time, is to keep one another around awhile longer. First they have to find Chas, Jess's loser boyfriend; Maureen proves her queenly stuff by taking a slug at him. Then there's the angel sighting that Jess invents for the tabloids -- Jess, who naturally turns out to be the daughter of someone famous, with more pain than anyone could guess. The plot that follows is outlandishly farcical without getting too complicated, which is just as it ought to be: The real story here, the undercurrent that contains and carries the narrative, is what the characters evoke in one another. Their individual stories unfold layer by layer, drawn out in dialogue or stream-of-consciousness soliloquy, each one's past more complex and equivocal than any single suicide note or decision could ever begin to capture. Maureen's is the story around which the rest evolve: a life of such kindness, suffering, and circumspect measures that it finally reduces even Jess to silence. ''You get the weight of everything wrong," Maureen says, half-apologetically, about what it's like to care for a severely brain-damaged teenage son. ''You have to guess all the time whether things are heavy or light, especially the things inside you, and you get it wrong, and it puts people off."

''A Long Way Down" is an act of such supple ventriloquism that it's almost spooky: You realize halfway through the novel that everything you know about each of these people -- their physical and emotional presence -- has been evoked by the others' perceptions, and that in itself is a marvel, because they're so acutely realized. If Maureen is the moral center of the novel, JJ, with his half-lousy dreams and self-deprecating shrugs, is its Nick Carraway-like observer. He reads all the modern sad guys -- Richard Yates and Raymond Carver and the like -- and finds, happily, that he has yet to read ''Martin Chuzzlewit"; the most accommodating of the bunch, he invents a non-punishing God for Catholic Maureen whom he calls Cosmic Tony. Jess, who modeled her imaginary angel for the tabloids after Matt Damon, slips us an inadvertent line of Philip Larkin -- ''they [epithet] you up, your mum and dad" -- though she'd be loath to admit it. And Martin plays the requisite role of fool: wry and secretly kind and too smart for his own good, except when it comes to himself. If he had one piece of advice for anyone, it would be brief: Take the stairs.

Even the title of ''A Long Way Down" is smart and funny; like most of the truths about life, you learn that the hard way round. The good news about Hornby's novel is that there are no happy endings in sight to sully its credibility: no sunsets, easy answers, mystery lovers who promise to make everything all right. Just the fact of another day, perhaps in the company of Dickens, or with the terrible, lovable Jess, or with this whole infernal ground-zero support group. For a story that begins with one foot off the cliff, it's hard to imagine a novel more darkly and sublimely devoted to life.

Gail Caldwell is chief book critic of the Globe. She can be reached at caldwell@globe.com.