This is a difficult book to review. I don't even want to say much about the plot because I feel like you should go into this book not knowing anything about it. It's good to know very little so you can be somewhat on even grounds with the main character, Bruno. Mind you, if you're old enough, you'll end up knowing more than Bruno ever came to knowing soon enough.
John Boyne is brilliant in making a story like this, a story of such heavy subjects, through the eyes of a child. It makes it that much more... important, I feel. It's simplistically written yet has a beautiful charm to it that really captures the reader in what this story has to tell. And it's nothing happy, let me tell you.
I highly recommend you read this book. It's quite a heartbreaking story, but an important one at that.