If you enjoy mysteries with girl sleuths, here are some other titles you may like:
Sammy Keyes and the Hotel Thief (a series!)
by Wendelin Van Draanen
The day before starting seventh grade, Sammy peers through her grandmother's binoculars and spots the latest in a rash of burglaries. The burglar spots her right back!
The Night Flyers
by Elizabeth McDavid Jones
In 1918, caring for her family's homing pigeons while her father is away fighting in World War I, twelve-year-old Pam comes to suspect that a mysterious stranger in her small North Carolina town is a German spy. Part of the History Mysteries series.
The Dark Stairs, A Herculeah Jones Mystery
by Betsy Byars
Herculeah and her side-kick, Meat, attempt to solve the mysterious disappearance of the owner of Dead Oaks, an estate with a history of murder and insanity.
The Secret of the Mansion by Julie Campbell
Thirteen-year-old Trixie Belden and her friends search for hidden treasure in a mysterious mansion owned by an old miser.