Real Friends by Shannon Hale (ages 8-12)

When best friends aren't forever... 

Shannon and Adrienne have been best friends ever since they were little. But one day, Adrienne starts hanging out with Jen, the most popular girl in class and the leader of a circle of friends called The Group. Everyone in The Group wants to be Jen's #1, and some girls would do anything to stay on top . . . even if it means bullying others.

Now every day is like a roller coaster for Shannon. Will she and Adrienne stay friends? Can she stand up for herself? And is she in The Group―or out?