Ventus by Karl Schroeder

A terraforming experiment gone wrong has left the world "Ventus" controlled by powerful nanotechnology AI who tolerate humans only as long as they avoid technology and other activities which affect the natural balance. After almost a thousand years the inhabitants of the planet have regressed to a medieval existence and regard the winds as godlike magical creatures.  Events in the wider universe have brought Ventus back into the spotlight of outside forces however.

This is superior Sci Fantasy from an author who is new to me. I downloaded this book because it is free under the creative commons license but there is nothing amateurish about it. I will be looking for more from Mr. Schroeder.