Eric Nelson, executive editor at Wiley is a really smart guy. Of course I follow him on Twitter. Tonight, apropos of nothing, he dropped these helpful hints into the scrum (my guess is he's reading proposals and feeling frustrated.)
If you're writing a nonfiction book, here's a few questions to answer. Like, actually write them down.
#1. What is your best story, and how does it explain the larger argument of your book?
#2. What's a key distinction you draw in the book, and why has no one else drawn it?
#3. What's the key moment in the recent past that made the world the way it is today? (At least the part of the world you're describing.)
#4. Why now? What we do we know now, but didn't 6 months or 6 years ago?