The Books plugin comes with a Reviews post type that is linked to books. This allows users to add reviews for specific books, which are then shown below the details on an individual book page. The average review score is calculated and shown before the list of individual reviews. Specific parts of the view can be turned off in the settings, such as the score or the reviewer location.
The reviews also have a shortcode that can be added anywhere on the site. This code pulls a random review from all reviews that have been added to the site.
Recent Books Widget
The plugin come with a recent books widget which can be added to a sidebar or a footer on the site. The widget displays the most recent books that have been added to the site, the number of which can be configured in the widget options.