Writersoul,
I agree with your statement about the agelessness of books. Many of the books I loved as a kid are still great when I reread them as an adult. I used the age grouping so people who might take my recommendation will have some idea of the age floor for enjoying the books and to assure people of the relative kashrus of the content.
Do yourself a favor and reread Ender’s Game. It is a truly great book.