It’s 1973 and Ben Tomlin is thirteen-years-old when his parents bring home his new baby brother, Zan. Like most babies, Zan needs baby food and diapers, and can throw a serious tantrum when things don’t go his way. But unlike most babies, Zan’s tantrums can be epic and may involve biting that requires stitches. Because Ben’s new little brother isn’t a human baby but a baby chimpanzee. Ben’s parents are behavioral scientists trying to discover if human/chimp communication is possible through the use of American Sign Language. To test their hypothesis, they will cross-foster a chimp in their human family, raising him as their own and teaching him sign language. There’s only one problem. No one asked Ben if he wanted a half-chimp brother. At first he’s just creeped out by the whole idea, but then Zan begins to win him over with his ridiculous antics, sweet personality and voracious ability to learn. Soon it really IS like Zan is just another member of the family, albeit a messy, loud, needy one. So when the experiment takes a unexpected turn and Zan’s continued placement in his home is questioned, Ben isn’t able to turn off his feelings for the chimp like his rational, science-minded dad. He’ll do whatever it takes to protect his little brother—even if it means breaking the law or tearing his family apart.

What’s so gor-ge-oso about this book is how Kenneth Oppel parallels Zan’s physical and mental development with the growth of Ben’s emotional maturity. As Zan is taught to be human, Ben begins to see how adolescence and high school are very much like a wild jungle, where he will have to learn how to be a dominant male (making many hilarious mistakes along the way) if he wants to survive. And as Zan begins to act out against his human family, making his chimp side known, Ben begins to chafe against the absolute rules of his strict father, making his emerging young manhood known. Everyone in the novel is a fully realized character, from Ben and Zan, to Peter, the hippie grad student who Zan loves best and Ben’s mom, a scientist with a soft heart who provides the book’s emotional and moral center. You guys, I just cried through the whole second half of this book, it was so moving. (That may want to make you read it more or less, depending on whether or not you are as big of a mush as me:) I couldn’t believe how attached I grew to these fictional characters. I didn’t want the story to end, and wanted to understand where Oppel’s inspiration came from. So I did a little digging and think that Oppel probably based Zan’s story on this true story of a chimp named Washoe who was cross fostered and taught ASL in the late 1960’s. If given even half a chance, this fantastically crafted tale of what it means to be human will swing into your heart to stay.