From the backcover:

For Sabrina and Daphne Grimm, life hasn't been a fairy tale. After the mysterious disappearance of their parents, the sisters are sent to live with their grandmother - a woman they believed was dead! Granny Relda reveals that the girls have two famous ancestores, the Brothers Grimm, whose classic book of fairy tales is actually a collection of case files of magical mischief. Now the girls must take on the family responsibility of being fairy-tale detectives.
Their first case? A roller-coaster ride of an adventure to stop a giant from destroying their new hometown.

----

Interesting!