Selling books is an exercise in the Heisenberg Principle. One cannot predict that a book will do well, only the likelihood that a book will do well.
[You just know that from Breaking Bad-Ed]
Actually, Ed, in the early 2000s we read a lot about physics, bitch.
To minimize uncertainty we stick with what we write. That is, we write a lot of exploding tanks, tension filled cabinet meetings, etc.
Our first successful book was To Defend the Earth. This is a collection of short stories about alien invasion culminating in the Battle of Luna- say it folks, 'Space-Dreadnaught'.
We followed up on this success with To Survive the Earth. However, Heisenberg reared his ugly head, and the book bombed.
We really don't know why. To Survive the Earth has all the goodies, including a blockbuster battle story where the Indian Space Navy attacks the alien base on Ceres. So if you like that sort of thing...