Inspired by a chimpanzee raised by the author in a Manhattan apartment, this diverting if outlandish story centers on a baby chimp who comes to live with sixth-grader Rachel Stelson s New York family. Not long after fidgety scientist Bucky Greene furtively drops off Friday in the middle of the night, and begs them to keep him for a week and to say nothing, Greene is reported dead. Rachel soon realizes that someone knows Friday is residing with the Stelsons and wants to get hold of the chimp. Mundis, a comedy writer, is at her best with descriptions of the chimp: Friday turns out to be prodigiously gifted. He quickly learns to play solitaire on the computer, solve Rubik s Cube and dial the phone. And he causes merry mayhem in the school gym and at a toy store on several occasions when Rachel sneaks him out of the apartment in her backpack. The plot grows goofier, linking Friday s intelligence to genetically engineered bananas and Greene s death to the evil motives of his bosses at the Bio-Allmeans research lab. Balancing the effective humor, a wistful undercurrent Rachel s mother died three years earlier fans into a bittersweet conclusion. A good choice for animal lovers. Ages 8-12.