Discussion Topics for Non-Fiction Authors?

I think I'm reasonably good at coming up with discussion topics of interest to Fantasy and Science Fiction readers and writers. I think I manage to find a few things of interest to other writers of fiction (setting, character, plot, viewpoint...). But when it comes to non-fiction I'm at a bit of a loss.

Are there any topics that will get Non-fiction authors talking about the whys and wherefores of what they do?

Are there generalities in non-fiction writing beyond spelling and grammar?

What about cross-overs between fiction writing and non-fiction writing? What skills do both types of authors have in common?

Quick brainstorming:

- Methods/topoi for organizing text (as contrasted with the plot, setting, and character of fiction).
- Academic versus popular approaches
- description versus prescription

>2 paradoxosalpha:
Description vs Prescription sounds like an awesome name for a thread. :)

And it made me think of something that is clearly a shared skill: Description.