There's no doubt that Life of Pi follows in the footsteps (or wake) of the great high-seas adventure novels. Its author, Yann Martel, spent a year and a half researching (along with religion and zoology) disaster and castaway stories (Yann Martel, "How I Wrote Life of Pi"). The book itself references many of the great adventure novelists like Daniel Defoe and Robert Louis Stevenson, in addition to historical castaways.
So what happens when you blend fiction and reality? Well, it depends. If you're like Martel, and your fictions are out-of-this-world stuff about tigers and carnivorous islands made of seaweed, then you end up with Magical Realism. In Magical Realism, the author retains a basic level of realism – a lifeboat, hunger, animal instinct – but inserts fantastical elements. Like the random French castaway Pi meets near the end. Or that island with all the meerkats.
Just for kicks, Martel allows Pi to relate the "real" version of events at the end of novel. This, friends, is a very postmodern move. (We mean "postmodern" in this sense: that versions of reality (e.g. stories) have replaced reality itself.) Martel wants to stress how humans create our own "realities," as well as how religion, or fiction, often tells the more attractive story. In essence, there's no such thing as a single true story. Humans often choose the richer story. Although the richer story may not line up with the factual events, it often communicates our humanness in a way the straight facts never could.
Martel doesn't reinvent prose like James Joyce, but he still aims for some fairly lofty goals. He's taken the genre of Magical Realism and, through a real humdinger of a plot, asked his readers some tough questions. Do people believe in religion – and sometimes in fiction – because they tell a better story? A more magical story? Is there anything wrong with that? Because Martel discusses these questions at length – through, of course, Pi Patel – the book also fits neatly in the genre of philosophical literature.