I came to this book having read The Book Thief over a year before (it became one of my favourite books of all time). If this sounds familiar, try to allow some leniency and understanding in knowing that 'I Am the Messenger' precedes Book Thief; it is probably hard for most people, including myself not to compare the two. Having said that, I'll try to review 'I Am the Messenger' on its own merits, without drawing too many comparisons.
So, overall this was a very well written, fun and sincere book. You definitely see Zusak's intelligence and storytelling ability through this book.
Ed is a flawed, yet highly likeable guy. He has a genuine (raw) beauty that you don't see in many characters in today's books and I loved that I actually felt the emotions he went through - the tense situations, empathy for people in horrible situations and the beauty of helping his friends.
After a while you start to go what he's going through - days lost to nothing consequential, the feeling that your life isn't going anywhere fast. In a way, his friends are his saving grace and you come to love them and respect them, even with their flaws, in the way that Ed does.
This is a very Australian book; at times it almost feels more like a movie script than a book. Some of the references, particularly closer to the start of the book are very Occa, and not everyone from overseas will understand the references and humour.
While this book is aimed at young adults, I think adults will appreciate it as well (if not more) and some of the themes are definitely for older youths anyway.
(SPOILERS WARNING) I note that some people are disappointed by the ending. I am somewhat, it kind of feels a bit like an easy cop-out on Zusak's behalf but then I also see beauty in it... I think really he's just trying to say that we can write our own story and improve on it if we just try... After all, if a somewhat downtrodden guy like Ed can do, anyone can.
Anyway, in conclusion, this book isn't another Book Theif but it is fun to read, amusing and I got some interesting ideas to think about by reading it.