I'm going to tell you a secret...I'm assuming that it's just the two of us anyway and I won't tell anyone, so if it gets out, I'll know who it is.
I can't write novels. It's not the writing that's the problem, or the stories, it's the length. Take A Baby's Bones, which I'm working on at the moment. I'm forty thousand words in and I've already identified one of the skeletons in the well, dropped one of my students down the same well, nearly split up a couple and they have reunited. Given the natural tendency of novels to speed up towards the big finale, I'm going to finish at under 60k, which is too short for a novel. This happens every time. I naturally write novellas or at least, very short novels.
The book I'm hoping my agent will be able to sell is really two books. One is a contemporary story (60k), one a historical (40k), and you might think I was trying to be clever stranding two narratives together (I may suggest so in my dissertation rationale!) but honestly, I didn't have much choice. I really can't pad a book out just to get to a word count. Fortunately I have another strand for A Baby's Bones. Borrowed Time 2 naturally has two narratives. But it's a question I've been asked a lot. How long is a novel?