Setting up a Required Add-On Item

 

This configuration makes it impossible for the user to skip selecting a book; i.e., the user is forced to choose one or the other. (Notice there is no "#Select a Book" row.)

 

Including a Choose One Line

If you want to include a Choose One line on a required option (to make sure customers choose the option they actually want, rather than the default option), you must include an asterisk (*) in front of the group label.

One Item Required Options

If there is only one item in the group, you must add an asterisk (*) in front of the group label to indicated this is a required choice. With the asterisk the option is always added when this product is ordered. Without the asterisk, the user can optionally add this item when they order this product.