I agree with Sebastian in that I'd like to see more meta-rules. How to design your OWN Prestige Classes, for instance. How to balance the creation of new spells, new feats, etc.
Sebastian wrote:
Just to elaborate a little more, I think the way to avoid rules bloat is to provide books that are better tools and less catalogues of cool stuff. There's a ton of cool stuff out there, but much less in the way of design guidelines or behind the scenes explanations of how to do stuff.
I also would love to see a book explaining how an adventure path is designed. What's the process for generating ideas, what are some considerations in designing cool climaxes and bosses, statting up new monsters, making a single monster survive long enough to challenge the party, how to tailor particular adventures in the path to fit the abilities of certain classes/races, etc. Something very practical and concrete, not at a high level and abstract ala dungeoncraft. Ideally, such a book would dissect an existing adventure path.