When first getting acquainted with the output of the "how-to-be-a-writer" industry, I read on a number of occasions that it commonly takes something like a half dozen manuscripts and ten years to get a book published--or at least, to write a "publishable" book.1 Such data as I have seen since then has convinced me that they were not all that far off the mark.
Of course, the reason why this is the case is that it takes such time to hone the relevant skills to the necessary degree. After all, novel-writing not only demands the skills associated with fiction writing in general (like the ability to tell a story, describe a scene or develop a character on the page), or writing in a specific genre (like the ability to create suspense that a thriller writer needs), but their exercise on the larger scale required for a book-length story, which means a writer's managing a number of interconnected subplots, coordinating a larger cast of characters, and overall presenting the broader field of view and deeper detailing that go with the form. The differences are not just quantitative, but qualitative, and entirely new and different skills are involved.
Still, those would-be purveyors of advice never said why it should take so long to pick these up. Rather, as I slowly learned, the answer laid in what they didn't say. Search as I might in the how-to books for some tidy explanation of what exactly one has to do to produce a hundred thousand word narrative, I never found it--because writing is more art than science, with little lending itself to formulas, and even the apparent formulas of little use in themselves.
Compare, for instance, the position of an English student learning how to construct a functional sentence, and another English student learning how to write a thesis statement. In the former case, the issue is reducible to the expression of a complete thought with a main clause containing a subject and predicate, accompanied by the appropriate punctuation and connections (e.g. capitalize the first letter of the first word, use commas to connect your clauses, finish with an end mark)--something one can execute and judge with almost mathematical precision.
Alas, no explanation of how to write a thesis statement is as compact and tidy as that. In the best of cases the student is given not a clear-cut prescription, but a theory of what constitutes a thesis, likely to be a much more complex thing (e.g. "A thesis is a claim about a topic with room for debate, based on a rational analysis of the facts"). One can, of course, judge whether or not someone has written a thesis in a reasonably objective way, but actually assimilating what it takes to produce one is a much more demanding thing, reliant on a good deal of intuition, personal observation, and learning by doing.
This is all the more the case with the writing of fiction. One typically learns to write novels by groping their way toward an understanding of the form, which typically comes less from the digestion of pithy advice than from reading a good many such works, and then by actually writing novels. The sheer length of a novel means that this is a slow process, a single first draft easily the work of months or years, without counting in the irregular and nonlinear pre-writing process, or the editing and revision that inevitably caps a serious effort. And of course, just as in the mastery of any other skill, several repetitions of the task are likely to be necessary before the result becomes tolerable.
Moreover, the process tends to be extended even beyond the amount of time it takes to write the requisite hundreds of thousands of words for several reasons.
One is the likelihood that the aspiring writer is unlikely to have their training process financially supported. This means that they are likely working at something else for income, which reduces the number of hours--and especially fresh, energetic, clear-headed hours--they can allot to their writing. (I know of one novelist--with a day job--who writes two hundred words a day. He will necessarily be less prolific than someone who, able to commit themselves to this full-time, can put in two thousand.)
Another reason is that one does not necessarily jump from one novel to the next. There are inevitable gaps, just as in any other course of work--because life gets in the way, and because, contrary to the celebration of stupid persistence so congenial to the self-help culture, a writer does sometimes need to go and do something else. People can get burned out writing, just as they can get burned out doing anything else, and the problem is exacerbated by the setbacks and disappointments with which the process is fraught--especially when one is not just writing, but pursuing publication. Submitting one's own work is not just time-consuming (and remember, any time in which one is submitting queries is time in which one is not actually writing), but typically a disspiriting activity that will frequently have the aspirant licking their wounds-- again and again and again, for many years.
It doesn't help that the learning process tends to be lonely. Yes, we all hear tales of people gifted with wonderfully supportive friends and family, but the reality is that people who are not writers generally do not understand what writers go through, and rarely have much sympathy for their tribulations (as the writer tends to find when they need to vent). Authors do command a measure of respect if they get rich and famous (despite which even the rich and famous have their insecurities and frustrations), and loved ones will likely put up with one who is at least paying his bills with his writing--but an author who is as yet unpublished tends to be treated with suspicion and contempt, as a malingering pseudointellectual who ought to be doing something more "useful" with their time. This doesn't help one's efficiency.
Unpublished authors also suffer in another way from that isolated position. Unlike an established writer with access to agent and editor and a slew of friends in the business, they do not get the benefit of personalized, professional advice. They may not even have anyone who can be a willing and able sounding board for their ideas, let alone offer meaningful feedback on their manuscripts. This leaves them having to figure out much more for themselves, doing much more of their own editing (another dispiriting activity), and makes them that much more likely to squander a lot of time and effort on artistically or commercially dubious ideas.
And so a decade goes by, just like that.
Of course, some writers do not need a half dozen manuscripts or a decade to reach the point at which they write "publishable" novels. Why the difference? Exceptional talent is always one possibility, though I am doubtful that talent spares anyone who actually pursues this course from having to suffer through a great deal of drudgery and frustration. A more likely possibility is that the author came to their first manuscript, or their third, with their skills relatively well-honed by other activity. They have already read more and written more than their counterparts by that point, and so are better-equipped to make the attempt. (Certainly a writer who pens their first novel-length manuscript at fifteen is likely to produce something quite different from what they would have written at twenty-five or thirty-five, especially if they have been doing other kinds of writing in the meantime.)
Some writers also get lucky, sidestepping a good many pitfalls without even knowing it, or learning more from their mistakes, or bouncing back more quickly from their failures, or having good fortune in their advisers, their personal support system, their access to privacy and quiet, or even the quantity and quality of leisure time they are able to devote to the effort. Some also get lucky in having a subject that makes the work easier, one that brings them closer than others to the ideal of "the story that writes itself." And some are fortunate in not having to go all this way on their own, but being able to get an agent or a publisher to take on a relatively raw manuscript, which they get to fix up under the close guidance of the pros, who are there for them again on the next attempt.2
Unfortunately, good luck is not a career plan.
1. Of course, publishable books often do go unpublished--while books that some might deem "unpublishable" do make it into the mill, and even reach the bestseller lists. The concern in this post is solely with the problem of writing a passable manuscript, getting published being an altogether different matter.
2. One other possibility is that the difference is not in the amount of work put in, but in the ways in which authors number their manuscripts. One writer may count the fifth massive rewrite of his first manuscript as still that first manuscript, while another might regard it as his sixth effort.
Actual Data on SF and Fantasy Publishing