The Weight of Silence, by Heather Gudenkauf
In this quiet, easy read, seven-year-old Calli Clark is best friends with Petra Gregory. Although Calli does not speak, Petra speaks on her behalf. Calli's father is a mean drunk, and her mother tries to pretend that everything is normal.
When Calli and Petra disappear early one morning, Calli's mother Antonia is forced to face what she has been trying to ignore.
Gudenkauf portrays a family damaged by alcoholism and abuse, with two sensitive children who have been deeply scarred by the disease.