This new mystery-puzzle series, three stories to a paperback volume, emphasizes the puzzle component. An ""introduction"" alerts readers to look for clues in the text and pictures, and each story breaks off with the kid detective's ""aha!"" revelations; solutions are appended, Encyclopedia Brown style. In two of these, Flute Revenge and The House on Blackthorn Hill, sister-brother team Amanda and Sherlock solve ""Hidden Clue Mysteries"" (as the series is called) in a variety of settings: ocean liner, race track, lobster dock in Maine, and their own comfortable neighborhood. The other two volumes, called ""Hidden Clue Codebreakers,"" are similar except that a code of some sort is involved in each one: an antique dealer-stealer communicates with his accomplice via classified ads; house painters communicate with their burglar partners by painting window panes in patterns that correspond to the addresses of empty houses; and Sherlock, kidnapped because he has stumbled across bait-store owner Mr. Nelson burying explosives on the beach, leaves groups of objects around the bait shop for Amanda to interpret. Smarter than we are, Amanda figures out that a plant mister, a box of nails, and a bottle of sun screen signify ""Mister Nelson,"" and a bait can, oar, and decoy (duck) mean ""bait store, dock."" Most of the others are easier to figure out, but all challenge readers to look sharp. And Bromberg plays fair in all four volumes: the clues are as available to vigilant readers as they are to Amanda and Sherlock. If the culprits' behavior is as unlikely as in other easy-to-read series--a stranger thwarted in the act of emptying Grandpa's lobster traps continues to harass and threaten him for decades to come; and a department-store baker robs the jewelry counter wearing his conspicuous apron and tall white chef's hat--these are exercises in detection, not psychology (or in suspense). And as detection, they proceed just as would-be sleuths would like their own cases to go. They could prove addictive.