The Changeling — Zilpha Keatley Snyder

Shy, quiet Martha Abbott isn't sure where she fits in. Her family calls her Marty Mouse because she's so timid, and she's never been popular at school. It's not until she meets Ivy Carson that things begin to change.

Ivy opens up a world of make-believe for Martha, and teaches her to be her own person. Even though no one approves of Ivy, who comes from a troubled family, Martha accepts her friend without question.

Each girl brings something special to the friendship. Can pressures from other people take it away?