TEENS: Good books for a 7th grade girl? Read details please?

Ask your librarian. Consider some of the clic science fiction--Andre Norton, Mercedes Lackey (try the Valdemar series) Isaac Asimov. Look at some of the historical mysteries, like Sharan Newman or Ellis Peters. Some stories combine both, like "I, Robot. You might like some stories set in different times or lands, like Alan Gordon's Fool series ("The Queen of Jerusalem is one"), or Margaret Foster's historical mysteries. Ask your librarian to help you find these authors or others like them.