There is nothing wrong with using a business card to promote your book: business cards are easy to carry and they tell people the most important information about your work – the title, author and where to buy it.
But that’s about all that they do.
If you want people to actually start reading your work, you can offer a free digital sample through Amazon.com or give away a PDF through your website. But when you are talking about your work to someone face-to-face, getting them to download a PDF isn’t always an option.
According to accountancy firm Deloitte, 80% of all book sales in the US in 2015 were print (that is, hard copies).
As we said, there is nothing wrong with using a business card to market your book, but if you want to get people reading your work right away, why not just hand them a printed sample?