A family of small folks -- bowler-hatted, Ziggy-like people -- lives in the roots of a tree. One day a human-sized couple drives up in a shiny red vintage car called Ruby and has a picnic. Seeing a year's worth of food in the open picnic basket, tiny Kevin goes scavenging. He gets trapped in the basket, so the rest of the diminutive family climbs onto the car in an effort to save him. They end up in the big people's garage, where Kevin is now stuck in a locked briefcase. They try every number they can think of until George, Kevin's father, realizes that the combination must be Ruby's license plate number. As the little people search for the lock combination, the reader is looking for the license plate number -- a challenge set forth by the author at the start of the book. The game is fun, and will continue to be even after the gimmick -- a sweepstakes in which readers can win the real Ruby -- is over. The joy here is in Thompson's (Pictures of Home, 1993, etc.) wacky drawings, which are filled with delicious details for adults (like book titles such as ""Nihilism for Beginners"" and ""The Wholefood Players' 'La Belle Dame Sans Meusli' ""). Ruby's history is followed pictorially along the top of each page, making this two wonderful picture books in one.