City of Bone by Martha Wells

Nice fantasy with a somewhat science-fictional feel - it's set in a post-apocalyptic world, where the apocalypse was brought about by an unfortunate combination of magic and hubris. A blurb described the setting as "Arabian Nights" style, but I didn't get that at all, apart from the desert setting. Most of the world's water was destroyed in the magical disaster, and the paired struggles for water and for knowledge of the Ancients drive the society and the plot.