This is an interesting question, and somewhat open to personal interpretation, so I suggest writing down ways in which you thought it was remarkable in order to answer it. For myself, I found it remarkable for several reasons. The first is the amount of research that had to go into it; Martel has indicated that he spent a couple of years just doing the research on it in order to write it. He had to research several key factors: Zoos and animal behavior, religions, and at-sea survival stories. So, he spent a lot of time doing research to be able to write the novel itself. Then, his representation of life in the zoos, and various different animals and their behaviors is just so interesting. Then, to have a tiger on a lifeboat and to imagine how one would survive that situation is just a very fascinating proposal to me. To describe the survival conditions at sea with the various hardships, sealife, would have required a lot of research. And the result is just so interesting.
Another way the book is remarkable to me is how Martel ties religion into all of it. An initial reading of the book might leave one wondering why Martel spent the first third of the book talking so much about religion, and having Pi become involved in 3 of the main religions in the world. There doesn't seem to be much of an overt connection between that section and the next sections. But, if you think about what Martel was saying about storytelling, and tie the end of the story having 2 different versions into it, there is a connection. Martel wanted us to consider reality in all of its ugliness and brutality, compared to a reality that existed with the stories of religion. He compared reality to the non-animal ending, and life with religion and its stories to life with the animals, and really, which makes a better story? So, Martel ties it all together in the end, in a very interesting way. The fact that he leaves the ending open to interpretation in order to reflect the individual's choice of an ending, is a remarkable fact too. A lot of authors want to pick the ending and have control of it themselves, but Martel left it up to the reader. That is hard to do.
So, those are just my thoughts; I hope that they jive with some of your own. Good luck!