This is one of those books that reminds me of why all adults should visit the Children's Department every once in a while. The questions asked by kids, and the answers they got from the Nobel Prize winners were touching, funny, odd, serious, and a few were kind of boring. But overall, this was a book to make you rethink your priorities.
The questions were simple (What makes the sky blue?, Why do we have to go to school?, What is love?) and the answers tried to make the complexities of these issues understandable. Sometimes they succeeded, others they didn't. The questions range from humanitarian to scientific to political, and so different chapters should definitely appeal to different readers. This would be a great discussion book - certain chapters would definitely begin some lively discussion and debate, either with parents, teachers, or librarians.
Evolution. Some religious discussion.