The Custom Fields tab enables you to add additional fields that you would like to show with each of your book reviews. For example, if you review comic books, you might want to show information such as artist or penciller.
Click on the Add Field button and then give your new field a name. Follow this step for every additional field you would like to add. You can reorder existing custom fields by dragging and dropping them to the desired positions:
When you edit a post, the custom fields you configured on the Custom Fields tab will appear in the Book Info section:
They will also be shown in the review box of a post: