Certamente você quer dizer o Ciclo do Death Gate . Há sete livros e você basicamente descreveu o primeiro. Eu comentaria isso para que alguém pudesse responder melhor, mas esta é minha primeira resposta, então não há repetição (e não há tempo suficiente para digitá-la).
Arianus, the World of Air, is composed entirely of porous floating islands, aligned in three basic altitudes. In the Low Realm, the dwarves (called "Gegs", an elven word for "insects") live on the continent Drevlin and cheerfully serve the giant Kicksey-winsey, a city-sized machine that is the source of all water in Arianus. In the Mid Realm, elves and humans have warred for centuries with each other and amongst themselves for water, status, and advantage. Above them all in the High Realm live the Mysteriarchs, isolationist human wizards of the Seventh House rank. They were some of the most powerful wizards of their kind, leaving fellow humans behind in their disgust for the constant warfare, but they never equalled the likes of the missing Sartan and Patryn races.
In the Realm of sky, humans, elves, and dwarves battle for control of precious water—traversing a world of airborne islands on currents of elven magic and the backs of mammoth dragons. But soon great magical forces will begin to rend the fabric of this delicate land. An assassin will be hired to kill a royal prince—by the king himself. A dwarf will challenge the beliefs of his people—and lead them in rebellion. And a sinister wizard will enact his plan to rule Arianus—a plan that may be felt far beyond the Realm of Sky and into the Death Gate itself.