Fiction: Three people arrive separately on the rooftop of a 15-floor building somewhere in North London.
Individually, each of them is committed to suicide, but each feels determined to save the others; it could be one of those infuriatingly recursive mathematical puzzles.
When a pizza delivery man arrives the stalemate is broken. Although the pizza is not for them - a moment of guilt here - they all sit down to eat, to listen, and to talk. What follows is a comic odyssey from the rave parties of North London on New Year's Eve to the cellar of Starbucks. It is no accident that the denouement of A Long Way Down takes place underground in a street called Upper.
The narrative unfolds in the words of each of the protagonists: Maureen, whose life, with her son, Matty, in his persistent vegetative state, has become unbearable for so many reasons, not the least of which is the iron fetter of her sense of duty; Jess, unstable and recently "dumped" by her "boyfriend"; Martin, ex-breakfast-show presenter, ex-tabloid journalist, ex-convict, guilty of abandoning a wife and family to screw a 15-year-old; and JJ the pizza delivery-man, an American whose band has failed and whose pointlessness seems the least convincing at first. Each in his way is a failed public personality with little or no interiority. All their failures, their hopelessness, their missed opportunities, their self-disgust relate, not to their sense of self but to how they are, or might be, perceived by others. Most pathetically of all, Maureen worries about what her son might think, even though he is incapable of response and perhaps even of perception. What saves them is belonging.
In a 1999 interview with Salon magazine, Hornby remarked that it was difficult to find people who are "100 per cent adult". There is no evidence in this book that he has been getting out more. Each of the characters in A Long Way Down is stuck somewhere in an unattractive and unhappy adolescence and each must, at some point in the narrative, begin the painful process of growing up.
The moment when they all sit down to break pizza on the roof of Topper's House is black humour at its best, full of baffled empathy and bile. Each tells his or her "story" in the time-honoured fashion of encounter groups, a kind of bizarre competition for the best - or worst - reason for wanting to die. The odds are against JJ the pizza man, but he pulls off a coup by lying, inventing a fictional brain disease called CCR, an acronym for the rock band Creedence Clearwater Revival.
Hornby, who has written a fascinating book of essays on popular music, never errs where music and musicians are concerned. That JJ is dying of CCR turns out to be an accurate diagnosis.
Unsurprisingly, there are surprises in store, twists in the plot and sudden reversals. None of these people is what they seem. Their pain is never simple. Their self-disgust is well founded if, also, tragic.
However, Hornby shirks the ultimate resolution in favour of a redemptive ending that must surely guarantee the movie rights. There is a rushed feeling to the final 30 pages or so, a breathless wrapping up, a sudden switch from, say, I Can't Get No Satisfaction to One Day At A Time.
There is, however, no sense of the weirdness of present-day Britain - the Kafkaesque arrest and detention of Muslims, the fear of even reasonable people that they will wake up one day to find Al Qaeda directing the traffic, the Asbos, the banning of hoodies - the impression of a vibrant country in the grip of a dictatorship of the paranoid. It is churlish, I admit, to complain that a work of black comedy is what it is, and not a political satire, but I kept wishing throughout a hugely enjoyable A Long Way Down that Hornby, with his scrupulous sense of the ridiculous, would turn his hand to both.
William Wall's fourth novel, This Is the Country, has just been published by Sceptre, and his second collection of poetry, Fahrenheit Says Nothing To Me, appeared in December from Dedalus Press
A Long Way Down By Nick Hornby Viking, 257pp. £10.99