HB – Publishers Weekly
While Ben and his family initially anthropomorphize Zan, Oppel doesn't, and as Zan gets older and stronger, the characters (and readers) are able to see an honest portrait of chimpanzee behavior, from the very best to the most brutal. Set in 1973, Zan's story echoes that of real chimpanzee studies of the era, though Oppel avoids dry factual recitations, or proselytizing when animal activism is introduced. Oppel's story is filled with compassion and has no easy answers.
– Publishers Weekly