Publishing books containing objects that have variants: When you publish a book in Author that has objects with variants, the publishing filter is displayed so you can select the variants for the job. The publishing filter is displayed after you have selected the book and the output type. One value can be selected for each variant criteria that is relevant to the job (click the value to display the button for the drop-down menu).
Publishing variant books: When you publish a variant book the variant objects used by the book have already been defined. In this case, the publishing filter is displayed but the values are predefined and cannot be changed (if you click the value the drop-down menu is not displayed).