The clue in the crossword cipher

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For cliffhanging suspense and thrilling action read THE NANCY DREW MYSTERY STORIES-the worlds most popular mystery series for young readers! Millions of fans have matched wits with Nancy Drew, helping her solve more than fifty baffling cases.
Detective and mystery storiesJuvenile literatureChildren's storiesDrew, nancy (fictitious character), fictionMystery and detective storiesChildren's fictionFictionJuvenile FictionMysteryOverDriveCollectionID:NDMS