Can you write a good novel in thirteen weeks? I don’t know. I can. The shortest time I’ve taken to write a novel was three days, which so far happens to be my best-selling novel. (Alas, work for hire.) And I’ve written a novel in five years. That novel remains to this date – deservedly and mercifully – unpublished. While the idea isn’t bad, it will take some serious rewriting to make it readable, the sort of rewriting that turns it into a trilogy and gives it new characters.
If you go on the evidence of the market, you’d do best to write a novel in a shorter time than thirteen weeks.
My average novel takes a little over a month, but I don’t count research and outlining and run up at the thing (which means finding the right voice and all that).
So thirteen weeks is probably about right, particularly since I’ll be doing my usual thing and writing other things in the evening, as well as editing a couple of other novels.
While it is tempting for the amateur to think that the quality of a novel is directly proportional to how long you take to write it, as far as I can tell there is no correlation. At least in terms of readability and salability — which is my definition of quality for this project — there were authors like Rex Stout, who had a long-lasting career and who wrote his novels in an average of a week per. There are also authors like J. K. Rowling, who is reported to have taken three years to write Harry Potter. There is of course Tolkien, who took more than a decade to produce his works. There simply is no correlation between quality and time.
You write a novel in as long as it takes to get the novel written. And that’s all there is to it. Even now, even in my case, some novels will appear to me fully-formed and with some I have to struggle for every word.