Kiki Strike - Inside The Shadow City

Life will never be the same for book-loving twelve-year-old Ananka Fishbein after she ventures into a hole near her New York apartment. Not only does she discover the mysterious Second City beneath the streets of New York, she is introduced to Kiki Strike, a black-clad, Vespa-riding, café-au-lait-drinking girl superspy.
Ananka joins Kiki as she recruits the delinquent Girl Scouts of Manhattan into an elite squad, the Irregulars, to fight crime and map the Second City. But someone else is after the secrets of the labyrinth below New York, and the cruel clique at Ananka's school has taken an interest in the Irregulars as well. When it seems Kiki can't be trusted, Ananka must take matters into her own hands, risking lives, secrets, and the safety of New York City itself.