The Fairy-Tale Detectives by Michael Buckley

Sabrina and Daphne Grimm thought their lives were complicated enough with their parents missing and them being placed in foster care. Until, a long lost grandmother shows up and they go to live with her in Ferryport Landing, New York. Ferryport Landing is a town unlike any other they have seen. Prince Charming is the mayor, Snow White is a school teacher, and the Three Little Pigs are the police. Sabrina and Daphne begin to learn their family history and how important they are to the safety of this town. The girls soon face stinging pixies, flying carpets, and talking mirrors as they set off on their first fairy-tale detectives mission to save their new grandmother from the clutches of a giant.