So, here I am, recommending it to you. It was first published in Zusak's native Australia as an adult book, and it was subsequently published in America as a children's book. Some of the themes are pretty gruelling (it is, after all, concerning Nazi Germany), but written in such a human way that they are not frightening. Still, maybe under-12s shouldn't read it...
I implore you to give it a try.
Here's the cover (picture from amazon):