Half Brother, by Kenneth Oppel

“On Ben’s thirteenth birthday, his parents introduce him to his new sibling: a hairy, swaddled baby chimp that will be raised as part of the family in an experiment run by Ben’s father, a behavioral psychologist. At first, Ben resists calling Zan his brother, but as he begins to communicate with Zan through sign language, he develops a true, loving connection with the little chimp, even as he realizes that his father views Zan as just a scientific specimen. What will happen to Zan when the experiment is over? … A moving, original novel that readers will want to ponder and discuss” (Booklist review)

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