When you work with variants you will often work in a single book, creating variants of topics or images for different variations of the document. This approach is used when you want to maintain the same book structure for each flavor of the document. Using this approach, any changes you make to the structure (for example, adding or removing topics) will be reflected in each flavor of the document.
Working with book variants
There will be times when different variations of the document require their own structure. This can be achieved by using book variants. You'll need to create variants of the book object, and if needed variants of any topic objects. You can then make alterations to the structure of each variant book as necessary - the alterations won't affect any other book.
You can also use book variants when you are working with sub books. When you work with variants of a sub book, ensure your master book includes the "primary" sub book. The primary sub book creates the relationship between the main book and the variant sub book. When you filter the main book the variant criteria are applied to the variant sub books as well as other variant objects.
The main book includes the "primary" sub book (which is used for one flavor of the document).
When the main book is filtered the primary sub book is swapped out and the variant sub book is used for a different flavor of the document.