What do you want to see in a campaign setting book?

[dangerous jack]

For me, what I want is simple: Each chapter (and preferably each page) should answer the questions:
* what distinguishes this campaign setting (or region within the campaign setting) from others?
* how does this affect the game at the table?

History and fluff is fine, as long as it always relates back to the types of encounters and adventures that will occur. But if most of a chapter could be replaced by "yada yada yada" and have no effect on the game I'm playing, then it doesn't need to be part of the campaign setting book. Although it might find a home in Dragon, etc.

 

[Dannyalcatraz]

Another vote for Maps & Fluff. A smattering of important NPCs, with stats.

However, one thing I'd like to see in particular is something we saw in 3Ed FR, which is mechanical options that make PCs from one region different from others. In 3Ed FR, it was done with Regional Feats.

Take those, and perhaps even add in some magics that were developed in the region (or by organizations within those regions- Red Wizards of Thay, anyone?), kept secret from outsiders.

That way, when someone makes a PC from region X, they will be able to make sure that anyone familiar with the setting could see from the PC sheet or seeing it in play would know that the PC hails from that region.