Mercy on These Teenage Chimps by Gary Soto

On his thirteenth birthday, Ronnie woke up feeling like a chimp—all long armed, big eared, and gangly. He's been muddling through each gawky day since. Now his best friend, Joey, has turned thirteen, too—and after Joey humiliates himself in front of a cute girl, he climbs a tree and refuses to come down. So Ronnie sets out to woo the girl on Joey's behalf. After all, teenage chimps have to stick together.
Acclaimed author Gary Soto tells a fun and touching story about friendship, understanding, and the painful insecurities of being thirteen.