I just gave The Book Thief to one of my younger cousins for Christmas - trying to spread the love, as it were. I remember reaching the end of the book and feeling like I'd been hit by a train. It's such an intense book. It's decent length, but there is no page wasted. I'm pretty sure I cried at least once. I also learned a good few German swearwords that my German teacher in high school forgot to mention . . . :)
I am the Messenger is also an awesome book, but entirely different. I got into The Book Thief through it, and was pleasantly surprised to find a very different kind of story - although they do both have that warm-cold-bright piercing quality to them that makes you want to run around the house dancing and crying. It's a bit more surreal in some ways, compared to The Book Thief, but set in current history. I hope he writes some other stuff soon, because I find it kind of disappointing that these are the only things he has written as far as I can tell :(