You should have already followed the Adding a custom dashboard widget recipe to have a starting point for this recipe. Alternatively, you can get the resulting code (Chapter 10/ch10-book-review-dashboard-widget/ch10-book-review-dashboard-widget-v1.php) from the code bundle and rename the file ch10-book-review-dashboard-widget.php. You should also have access to a network site configured as a Network to test all of this plugin's functionality.