Kind of ass-backwards to some, but in my development of the Kaidan setting of Japanese horror (PFRPG), at the start of that project, it wasn't known whether creating an entire setting first was the most economical or smart way to start. Creating a setting is fairly expensive, so only a setting that is known to be a seller, is worth spending money on. Also along with this discussion of decisions surrounding whether to include a full or partial adventure - this is what I did for our first Kaidan product: the Curse of the Golden Spear was an introductory mini-campaign arc, a trilogy of modules (5th, 6th and 7th level).
Since Kaidan is an analog fantasy, feudal Japan, and this was an introductory product, and there is some expectation that the majority of people are not playing oriental race/classes. So this adventure was designed in mind for outsiders (standard, Euro-based flavored PCs) visiting the far east. Many/most of the unique setting rules might be known to locals living in Kaidan, but since the adventure is designed as an introduction, the assumption is that the PCs have no hidden knowledge of Kaidan, therefore is best represented by outsiders not from Kaidan itself.
All the unique Kaidan setting rules were placed in the appendices at the end of each adventure. We included 3 unique Kaidan mechanics or aspects with each adventure, thus 3 items in each module appendix. This way we didn't have to create an entire setting guide before releasing an intro adventure. So these were 3 full adventures, as a complete 3 part mini-campaign, and all the major unique features of Kaidan are introduced in these modules - thus fully serving its purpose as an intro product.
Since that trilogy of modules, and subsequent creation of 4 one-shot modules, racial supplements and class faction books, Kaidan has built a solid fanbase, and only now (following a Kickstarter to support it 2 summers ago), we'll be shortly releasing the complete GM's guide to Kaidan, as well as a Player guide to the setting as well. More content and adventure material will be produced after the release of the setting guides.
This is the process at which we decided to release this line of setting material for Pathfinder.