How does that process work? Is one of you at the keyboard while the other one is over your shoulder saying do this, do this, or do you divide and conquer and then hand each other the stuff?

It was a lot of divide and conquer. Usually it would just be like, hey, you grab this chapter, I'll grab this chapter, whatever, and then do a draft, swap, give notes and rewrite it.

We don't usually sit and hammer stuff out at the same time.