Why are there two endings to the novel?

This is one of the points of the novel. Was Pi imagining his animal friends or was it all real? Were his animals on the boat metaphorical or literal? It is much more interesting to view this story as literal rather than just Pi being in a dehydrated coma. Certainly the theme lends itself to our view of the world. The imagination and myth factor in Pi's story certainly gives meaning to Pi's life and world. This is much the same as how myth and imagination gives our own lives meaning and understanding.