There is another secret to selling lots of books: writing lots of books. We asked best-selling authors how many books they had written. Here’s what they said:
Nine out of ten best-selling authors have published more than one book. More than half have published ten or more books.
Writing lots of books in one niche has many benefits. For starters, you don’t have to relearn your audience. And if you write non-fiction, you’ll also be able to re-use a lot of the research you did for your first book.