I love this introduction to the series from Alan Bradley's website:
Picture an ancient country house somewhere in England. The year is 1950.
Picture a girl who lives there with her most unusual family. Her name is Flavia de Luce—and she’s almost eleven.
Picture a long-abandoned Victorian chemistry laboratory; no one ever goes there but Flavia.
Put them all together and you’ll have a new kind of detective fiction . . .Flavia de Luce lives spends a lot of time in her chemistry lab, which was originally occupied by a distant relative whom she looks up to because of his science acumen. Although Flavia herself is becoming quite the scientist herself; She has a particular passion for poison. She also has a problem leaving any mystery unsolved. So when an attempted murder happens on her own property, she's the first one to begin the investigation. The local Inspector is not thrilled having a precocious, but accurate, eleven-year-old showing him up with clues and theories, but he begrudgingly takes her help.
This is a delightful mystery! Flavia will capture your heart early on and you'll be sad when the book ends. Not only is Flavia a delightful, snappy character but the dialogue is to die for. The tone of this series is part gumshoe detective, part proper British mystery. It's sharp, witty and seriously funny.
Alan Bradley has written several Flavia de Luce novels, but you don't need to read them in order. There are six so far and this is the third one. The series has its own website here. Check it out and pick one to begin the adventure.