The Wild At Heart series by Laurie Halse Anderson
American Girl books
The Babysitter's Club Series
Nancy Drew books
Sable by Karen Hesse
Harry Potter series
At that age I started reading a lot of classics in young-adult versions...like Jules Verne, Jack London, Dickens, Mark Twain, etc. I had a set my mom bought at KB Toys, but I believe there are other versions.