Kiki Strike is a very interesting read. I first read it when I was 11. I'm 14 and still enjoy it.
The book features Anaka Fishbein, and her quest for the Shadow City, an series of underground tunnels. She meets Kiki Strike, a pale girl with completely white hair. Kiki Strike tells her about the Shadow City, and they make a plan to rule it. Teaming with Oona Wong, Luz Lopez, DeDe Morelock, and Betty Benntt, they start exploring the tunnels.
The book has a very good plot as well as kidnappings, druggings, and explosions. While this is aged toward pre-teens, I happen to still enjoy it. It also has a suprise ending. However, the thing I love most about the book is that it has special pages throughout it, talking about the advantages to being a girl, how to tell if a diamond is fake, how to make the perfect disguise, etc.