Authors can also write book reviews and create book lists for other sites. If possible, ask the other site to mention your book. If people just see the book and author's name, a URL isn't absolutely necessary. They will now have something to search for if they are curious about you and what you have published. Create a Webring.
Many people misunderstand the benefits of webrings.
But a Webring acts like a specialized mini-directory. People will look at the links in the Webring to see if the other sites appeal to them. It's a navigational tool which brings a small amount of focused traffic to member sites. They refuse to link to competitive Web sites. The World Wide Web is about connecting with other people of similar interests, not shutting them out.