I don't understand why this isn't insanely popular. An elite team is assembled from the ranks of NYC girl scouts: a master of disguise, a chemistry (explosives) experimenter, a forger, a researcher, a builder-of-useful-devices. Because the thing is: no one suspects an eleven-year-old girl. There's action, adventure, mystery, maps, exploration, history enough for half a dozen Nancy Drews, but with a modern, kick-ass twenty-first century feel.
Rollicking is the word I want. Gallagher Girls without all the romance stuff. Highly recommended to middle grade readers who like adventure and/or Alex Rider books.