Cast adrift on the Pacific Ocean, a 16-year-old boy and a Bengal tiger survive in a boat together, for seven months. Even sceptical critics have remarked how successfully Life of Pi persuades the reader to suspend disbelief. This strange story is made credible by the logical, sometimes pedantic, unsurprisable voice of its narrator. Yann Martel wants us to hear how odd this voice can sound. This is why his book begins with a framing narrative: a story about how the story that follows came to light. It says that the author travelled to India in the wake of an unsuccessful novel, published in 1996. (Martel's novel Self did appear that year.) There a man told him about Pi Patel, now living in Canada. The author went off with his notebook and found him. (Occasional short chapters in italic print recall meetings and interviews with Pi in Toronto.) The novel is to behave as if it were a record, transcribed but not invented by its author.
Pi's voice is a peculiar, cleverly achieved mix of articulacy and awkwardness, sometimes eloquent but often naive. Sentences begin with the redundant phrases of an ingenuous narrator: "The thing was ...", "I tell you ...", "I'll be honest about it ...". Controlling any sallies of fancy, Martel has made him comfortable with clichés. The occasional madness of living things is "part and parcel" of the ability to adapt; Pi's father sells his zoo "lock, stock, and barrel". In the extremity of his unlikely predicament, truisms seem to become truer. Describing his realisation that he must "train" the tiger to reach an accommodation with him, he explains: "It was not a question of him or me, but of him and me. We were, literally and figuratively, in the same boat." Just so.
Under pressure, the style becomes most flatly factual. The manner suits the survival story that this novel is. Presciently, it would seem, Pi's mother has recommended Robinson Crusoe to him, and Martel has certainly learned from Crusoe's "strange surprising adventures" (to quote Defoe's original title) how a shipwreck requires the hero to notice every physical thing that is left to him. A good survivor-narrator recalls for us exactly how each challenge is comprehended and met. The survival yarn is made compelling by the narrator's insistence on all the little details: what resources he had, how he collected fresh water, what fish he managed to catch - and how he calculated his behaviour to appease the tiger.
Like Crusoe, Pi is keen on inventories, the barest accounts of reality. What did he find on his lifeboat? "After a thorough investigation, I made a complete list." There follows a two-page catalogue. Listing is also his way of doing justice to the natural world, the consequence of growing up in the botanical gardens among "peepuls, gulmohurs, flames of the forest, red silk cottons, jacarandas, mangoes, jackfruits and many others that would remain unknown to you if they didn't have neat labels at their feet". The zoo proliferates with lists: lists of the animals and their peculiarities, but other lists, too. There is the painful list of the items that people sadistically feed to the animals ("ballpoint pens, paper clips, safety pins, rubber bands, combs, coffee spoons, horseshoes ...") and of the animals that have died from ingesting foreign bodies ("gorillas, bison, storks, rheas, ostriches, seals, sea lions ..."). There is the list of animals that Pi believes are living in Tokyo, right now - "Boa constrictors, Komodo dragons, crocodiles, piranhas, ostriches, wolves, lynx, wallabies ..." - if only you could shake the city out.
Animals divert his narration from the usual human channels. He is, on first reading, weirdly digressive, preferring zoological lore to human information. The novel is full of stories about animals, all calculated to destroy our illusions about their love of freedom or their human-like attributes. He avoids interesting us much in his family (his father is influential only inasmuch as he is keeper of the zoo). When his father, mother and brother drown in mid-Pacific he may claim to be affected but there is no feeling aroused in the reader. But then he discovers about human needs and fears through his animal observations. This is why it is important that he is a teenager, even if recalled many fictional years later. His innocence is a formal necessity. No adult could drink in the bright, frightening strangeness of the natural world.
· John Mullan is professor of English at University College London. All tickets for the book club event with Yann Martel on Wednesday October 3 have now been sold, but a recording will be made available at books.theguardian.com/podcasts