The big story this week has been the jumping of The Cuckoo's Calling from obscurity to number one on Amazon soon as it was revealed it was actually written by J.K. Rowling. As with most news stories, there are several angles. Let me present mine.
This situation is about as close to a controlled experiment as we are likely to see in the publishing world. A well-run experiment has three types of variables. Controlled variables are things that are kept the same. Independent variables are things that are changed by the researcher. Dependent variables are the results of the experiment, which are determined by how the researcher manipulates the independent variables.
In this case, the controlled variable is the story, which remains constant throughout. The independent variable is the familiarity of the author, which is changed from an unknown (Robert Galbraith) to the best known (J.K. Rowling). The dependent variable is the amount of book sales. By now, everyone knows the results of this experiment.
The conclusion is no matter how well you can write if no one knows who you are you will probably not sell many books. In an ideal world, the sales of a particular book are a direct result of how well-written it is and nothing else. We do not live in an ideal world.
Today's authors must be promoters of books as well as writers of books. A mediocre book that is promoted well will almost always sell a lot more copies than a well-written book that is promoted poorly. It may not be right or fair that a writer must learn to promote himself and his works, but that's the reality we are stuck with. Otherwise, you could be as talented as J. K. Rowling and still not sell many books.