At the age of 20, in his third year at university as a would-be physicist, Albert Lippincott discovers the deepest secrets of the universe. In a stroke of serendipity, he develops 'a genuine actual-size infinitely dimensional map of all realities of this universe and all others'. He is the vessel for the knowledge that would allow a transition from 'the age of incomprehension' to 'the age of understanding'. He knows this wisdom must be shared and he does this by trying to bite the eyes of his physics professor.

Be thankful for J. Robert Lennon's sense of humour, or this would be a terminally depressing book. Lennon's quirky, comic epic, set in small-town America, highlights the absurdities and little injustices we all have to live with, and illustrates how the quest for knowledge, particularly answers to big questions like how the universe works, can drive anyone mad. Yet seek we must, and some of us are more compelled than others. Some of us are like Mailman.

Mailman is Albert Lippincott. He's been a postman in an upstate New York town nearly all of his adult life. Every morning, he wakes at dawn but doesn't open his eyes because a war veteran once told him that he must 'always assume the enemy is watching'. Still keeping his eyes shut, he opens a container by his bed and counts out 20 grains of rice, which he chews slowly while he 'absolves himself of the previous day's mistakes'.

Readers will still be laughing at the 57-year-old little boy playing soldier when Lennon confronts them with the realisation that this is a middle-aged man who knows he's failed. Mailman is alone in bed, confronting his mistakes while keeping his eyes closed, shutting out the rest of the world.

But the world intrudes anyway, and Lippincott has to deal with the fact that his bosses seem to be on to his habit of 'borrowing' other people's mail for his own perusal. Then there is a painful lump growing under his left arm, foreshadowed by a disturbing hallucination. Before long he realises he has to confront more than the previous day's errors.

He must come to terms with his past: his latently incestuous relationship with his sister, his parents who seem to have read every Dr Spock book and did exactly the opposite of the doctor's advice, his tragically flawed romances, and his failure to live up to his potential. There's his pathetic attempt to wipe the slate clean by joining the Peace Corps, which sends him on a mission to reform the postal system in Kazakhstan.

Alienation underlies Mailman's seemingly endless but thoroughly entertaining rants.

Lennon is at his best when we are inside Mailman's head. He skewers God ('the perp'), journalists who think ordinary people care about stock reports, small-town politics, sports utility vehicles ('What's a lone man need with a giant machine like that?'), and the upper-middle class ('Winter is only a verb if you're rich'). Mailman's eccentric narrative voice might take some getting used to, but the payoff makes the slight effort worth it. Lennon refers to his protagonist only as 'Mailman' - apparently to highlight the anonymity of Lippincott and blue-collar workers like him everywhere. The device can initially be off-putting, but it works. His protagonist isn't Lippincott, it's Mailman, and Mailman could be anyone.

Long before the book ends, we identify with Mailman. His mediocrity is universal; his failings remind us of ours.

But Lennon also makes us realise the pointlessness of assessing one's life in comparison to others. Because no matter how successful you are, no matter how well you've worked or slept your way to the top, there will always be someone with a nicer car, a bigger yacht, smarter children, a knighthood, a more pristine private island.

On the upside, no matter how far you fall, you can derive comfort in the knowledge that there will be someone who has failed even more spectacularly than you have.