Glass God (Magicals Anonymous)

"Sharon Li: apprentice shaman and community support officer for the magically inclined. It wasn't the career Sharon had in mind, but she's getting used to running Magicals Anonymous and learning how to Be One with the City. When the Midnight Mayor goes missing, leaving only a suspiciously innocent-looking umbrella behind him, Sharon finds herself promoted. Her first task: find the Midnight Mayor. The only clues she has are a city dryad's cryptic warning and several pairs of abandoned shoes"--