For the first half of this book, I was in complete agreement with the decision to award Avi with the Newbery. Unfortunately, even though the story was still good for the other half, the hints and clues became so obvious that only a second grader could have missed the big "secret" of the book. What's more, I didn't feel like Crispin's transformation was very believable. The timeframe I understood really didn't allow for such a change, especially when the book was told in first-person and Crispin himself brushed over the details of how his character was developing.
That being said, I do think Avi picked an interesting setting for his novel, and did quite well presenting the way life would have been in that setting. If I were a second grader, I'd probably love the book. As it is...I like it. And that's good enough.