People apparently only read mystery stories of any length. With mysteries, the longer the better, and people will read any damn thing. But the indulgent, 800-page books that were written a hundred years ago are just not going to be written anymore, and people need to get used to that.
I started writing in my 20s. I just wanted to write, but I didn't have anything to write about, so in the beginning, I wrote entertainments - mainly murder mysteries.