I have some questions and suggestions for you:
Are these books self-published or did you get a publisher?
If the latter, what is your publisher doing to help promote your books?
Your advertising doesn't really say WHAT these books are - are they fiction? non-fiction? Is it about women and their relationships and lives and quilting is in the background? Do you use these characters to illustrate or teach quilting? I have to work too hard to figure that out from your website.
A sample chapter would go a really long way to helping me (and probably others) decide if these books are our cup of tea.
If you are self-publishing, having an affiliate program would likely help you - you can then get other people promoting your books and they would get a small portion of the sale price.
Also, the fact that there are 9 books in the series (so far) (and that's impressive!) is kind of scary - espeically if each volume is over 10 dollars -- that's a 100 dollar "investment" for someone to read all the books. lf you are selling hardcopy and these are hardcover or trade paper type books I suppose that price is justified, but remember you are competing with paperbacks that sell for significantly less.
I also didn't notice if you included a page count for the books - this is typically done.
Have you tried marketing on Facebook and Twitter? Do your books have crossover interest in other markets besides quilting?
"Guerrilla Marketing" involves activating your fan base to help spread the word and get your product known.
I've had an independent band and record label for over 10 years. marketing can be a full-time job.
If your books were instructional quilting books, I'd suggest that you hold workshops at various quilt guilds, and make the book part of the workshop (a few of our guild presenters did that and I picked up some nice books that way).
Feel free to PM me to talk more about marketing.