My thesis was just under 20,000 words. That was my undergraduate thesis. I have not been to grad school. Yet. It was (is if you want to read it) 288 words per page, just about the same as your average novel, which is 250 words per pages. So, I wrote about an 80-page book.
According the interweb, 7500 to 20,000 words is a novellette, which is smaller than a novella, and just bigger than a short story, which is 1,000 to 7500 words. A novel is about 50,000 to 100,000 words. Anything bigger than that, no one wants to read, basically.
So, I am capable of writing a novellette. I’ve done it. It took all I had at the time, but it was also an academic paper, which I have since learned is not what I want to write. 🙂
It just takes persistence. Maybe a little creativity. But at this point, persistence.