Walk Two Moons by Sharon Creech

Don’t judge a man until you’ve walked two moons in his moccasins. What is the meaning of this strange message left on the doorstep? Only Sal knows, and on a roadtrip with her grandparents she tells the bizarre tale of Phoebe Winterbottom, Phoebe’s disappearing mother and the lunatic. But who can help Sal make sense of the mystery that surrounds her own story .

. . and her own missing mother?