The Killing Moon

FOLLOWING HER SERIES, HUGO, NEBULA, AND WORLD FANTASY-NOMINATED DEBUT SERIES, N. K. JEMISIN RETURNS WITH A CAPTIVATING NEW TALE.

In the ancient city-state of Gujaareh, peace is the only law. Upon its rooftops and among the shadows of its cobbled streets wait the Gatherers--the keepers of this peace. Their duty is to harvest the magic of the sleeping mind and use it to heal, soothe...and kill those judged corrupt.

But when a conspiracy blooms within Gujaareh's great temple, Ehiru--the most famous of the city's Gatherers--must question everything he knows. Someone, or something, is stalking its prey both in Gujaareh's alleys and the realm of dreams. Ehiru must now protect the woman he was sent to kill--or watch the city be devoured by war and forbidden magic.

This description comes from the publisher. The Killing Moon is the first book in the Dreamblood Duology.

Synopsis from Open Library.