How many projects do you have to write before the big one?

Writers often get asked how many books they wrote before they got one published. I think the typical answer is around four (I vaguely recall someone compiling statistics on this, but it's also my experience anecdotally, from talking to other writers). I do know writers who have sold the very first book they ever wrote, but they are the exception.

I have a tough time answering this question, because it depends on what you mean by "write a book." I started writing little stories as soon as my fi...