I asked someone who has been successfully marketing books for years what three things she would suggest to book authors who wanted to sell more books. She said:
a) Get 100 interesting and diverse Amazon Reviews from friends, colleagues and fans.
b) If you have a nonfiction book, do live or virtual workshops every month continuously
c) Build a real base of (your book title) fans on Twitter and/or Face book.......5,000 would be a great goal