Pilkey bridges the gap between his picture books and "Captain Underpants" series (Scholastic) with this entry about Ricky the mouse and his mechanical pal. Here, the duo battle extraterrestrial insects and an evil robot. In addition to telling an amusing story, the author also manages to squeeze in factoids about the planet Mercury, Flip-O-Rama animation, and cartooning lessons, though these may prove difficult for the targeted audience. Ontiveros's black-and-white cartoons enhance the humor and action, and the layout breaks the text into manageable chunks for new readers. This series may not be as popular as Pilkey's earlier titles, but Ricky will garner young fans of his own. Laura Santoro, Coventry Library, Cleveland Heights, OH Copyright 2000 Reed Business Information, Inc.