City of Bones — Martha Wells

Where once great galleons roamed the seas,
sand ships now traverse the Great Waste,
and a glittering chain of city-states
dots the desert that has no end....

And the greatest city of all is Charisat: Imperial seat and wonder of wonders, a great monolithic structure towering over the desert. Charisat, a phantasmagorical place where silken courtesans and beggars weave lies side by side, where any man's dreams can be fulfilled at the whisper of a genie, and where the tier that you live on determines how high up the food (or, more importantly, water) chain you are. It is the goal of every schemer, treasure hunter and madman intent on finding his heart's content -- a place that dazzles the senses, makes the most somber mind dizzy with its scents and sights -- and where no one knows friend from foe when it comes to the desperate fight for dwindling resources.

And where a beautiful woman and a handsome thief will try to unravel the mysteries of an age-old technology to stop a fanatical cult before they unleash an evil that will topple Charisat.

And destroy all the water in the world.