Most authors run a website and blog, and you can put the link to your mailing list here to encourage readers to sign up. Ask people to sign up. Though mailing list you should never assume that a reader wants to be added, you can out right ask them if they'd like to join. If readers email you about your books, respond to their message mailing list and ask if they'd like to join your mailing list. Meanwhile, post in forums and blogs to make sure that everyone knows that this option is available.
Creating a mailing list is well worth the effort, and you can find that subsequent book sales start off with a bang; largely thanks to the avid fans on your database. Ever wondered if building your own mailing list is really that important? Well, it definitely is. The fact of the mailing list matter is, if you don't have a mailing list you are missing out on the most important piece of you business and the major search engines are leaving you out of the cyber space to find your own way out into the world.
We know SEO is a major lifeline of your business. But there is more to it than just search engine optimization (SEO). Having an online business without a mailing list, you are essentially leaving money on the table. It would be pretty difficult to mailing list maintain your business, whether it's online or an offline business without a customer base. Your primary goal in mind should be to have repeat customers who will stay with you and it's an integral part to stay current, relevant and top of mind.