. . . or All Around the Town with Encyclopedia Brown. New York City institutions substitute for Idaville backyards in these five mystery/puzzles (four of them reprinted from Boy's Life and elsewhere) and Asimov's smart, stalwart kid is named Larry, but he's as quick as Sobol's to solve his detective father's cases--finding the key word Dad needs to break a criminal code in the Times crossword puzzle; locating the museum's stolen coins by positing a far-fetched confusion between Santa Claus (Kris Kringle) and Christkindl (the creche in a nearby church); and--as any dinosaur freak will foresee when the jewel thief dying in the Natural History museum whispers "Try Sarah Tops"--turning up a missing diamond in the Triceratops skeleton. Clicking away perpetually and refusing all rewards ("I was only doing my duty"), Larry saves the Soviet UN offices from a threatened bombing by remembering that their Christmas day is our January 7, and--though he hates to put the finger on anyone--clears a classmate suspected of sneaking test questions by directing the principal to the real culprit, a female A student. Brisk--if you feel that the Apple flavoring warrants the new line.