Akata Witch by Nnedi Okorafor

Strange things start happening in Sunny’s life when her friends reveal to her that they have magical abilities and they suspect that she has them as well. Sunny discovers that she is a “free agent” of the Leopard People.  Besides her regular studies at school, Sunny begins learning magical history, juju, spells, and other magic with her three friends Orlu, Chichi, and Sasha.  All of this she must keep from her overprotective and strict family. Things become even more complicated when the four friends discover that they have been selected by the magical council to take on a serial killer.