Backmatter consists of your author bio, information on your other books (if you have any), your products or services or company, or even a free offer that drives readers to your website to sign up for your mailing list. (howtoblogabook.com)
I just started putting books out via Createspace and add all the kindle backmatter plus a teaser of sample chapters for other titles. (deborahjayauthor.com)