Dragon Kings is a rules-neutral RPG setting that’s up on Kickstarter now.
From the campaign:
This single 160-page hardcover volume (or PDF) presents Khitus, the world of Dragon Kings, as a complete role-playing game setting. It describes all the important nations and rulers, its guilds and sects, its landscapes and monsters — everything heroes must confront and deal with as they adventure across this formidable, desert world. The book is expertly written with full-color illustrations and maps from the experienced Dragon Kings Team.
The Dragon Kings World Book is rules agnostic. The information within can be used with different gaming systems, so you can use your favorite mechanics to play! Anyone who gets the World Book (in either PDF or hardback format) also gets all the different PDF Rules Supplements – these two are available to everyone on publication, and more rules systems may become available as Stretch Goals