He wants to be comfortable because he has some experience to share. Like with 'Expectations'. No, it's not Great Expectations, but the little expectations that readers have when they pick up a book with the label 'Crime Fiction' on it. They're looking for a Detective? Maybe. Like a cop or a policeman. Or maybe a Private Detective, not a Private Eye or a handsome hero. Whatever, you, the writer need to be thinking like a reader too, aware of what your little story might be looking like, before it even starts telling anyone anything.
Luckily we've got Mike here to explain it all. He can do it much better than me.