I keep up with What is Stephen Harper Reading and if you check out Book Number 76 you can see a scan of the note that Mr. Obama wrote to Yann Martel (link in the first paragraph).
If you haven't read Life of Pi I highly recommend it! It's not only my favorite book but I'm pretty sure it's the best book I've ever read. There are so many things I love about it but one of its best features is how much your personal experience can alter your interpretation of the book.
Also, here's a link about Martel's latest book.