New free addon for GD Rating System Pro, brings one more rich snippet type into the Rich Snippet support for ratings, this time for the Book Rich Snippet. The plugin has no settings, only extra control for defining the snippet inside the snippets post metabox.
This first version of the plugin supports Simple format for the book, essentially book listing with one or more offers. There are other variants of the Book snippet, and they will be added in one of the future versions.
The snippet fully validates in the Google snippet testing tool, but, it is possible that in the future Google will make more changes, and the plugin would need to be adjusted to compensate for whatever Google decides to change.