Black moon rising - D. J. MacHale

Marcus is an agent of the Library--a place filled with tales that don't have an ending. Mysteries that won't be solved until Marcus and his friends Theo and Lu step in to finish them. Before it's too late. Because mysterious accidents are disturbing a middle school in Massachusetts. Windows shatter for no reason. Bleachers collapse at a pep rally. Most of the students think they're just having a string of bad luck, but Marcus suspects something a lot more dangerous. Something like witchcraft. When the black moon rises, this story must come to an end . . . one way or another.