WHAT DO YOU HEAR WHEN COWS SING?

``Moosic'' is the answer to the question in the title, perfectly reflecting the goofy tone of this worthy sequel to the father-and-son team's first book of riddles, Riddle City, USA! (1994). Beginning readers will have their curiosity piqued by the inventive questions (``What are soft, white visitors from Mars?'') and more than satisfied by the answers (``Martian-mallows''). Funny illustrations accompany each riddle, with loafing bread, grinning bugs, and smiling ships. The Maestros have captured the silliness and wordplay children of this age enjoy; the bonus is that they can read them to each other. A great addition to the venerable I Can Read series. (Picture book. 4-8)