If you have a site that promotes your books (or anything else), there are ways other than social media to make people aware of it.
One that was mentioned recently at the elegant themes blog was "get physical." In other words, create something in the real world that points people to your site. They suggested t-shirts, posters, and putting your url on your business card.
A method I used when my book, Your Writing Coach, first came out, was to print small cards featuring tips on how to overcome writer's block, with a plug for the book and its accompanying web site at the bottom.
I offered these as a give-away to writing conferences, and quite a few took me up on it. We ended up distributing several thousand copies.
I don't know how many people actually bought the book as a result but I did get email from people who appreciated the tips, and the traffic to the site did increase.
You could also print bookmarks to distribute to bookstores. You may find that the independent bookstores are more open to this than the chains. The latter may want to charge for putting the bookmarks on their counters.
The key is being sure that whatever you produce is useful, not just an ad.
ps: Both Your Writing Coach and Your Creative Writing Masterclass are available from your favorite bookseller. Their matching sites are www.YourWritingCoach.com and www.YourCreativeWritingMasterclass.com.