Maybe you've written more than one series of books and want to see the sales just for one series, or maybe you write for multiple genres and want to monitor your sales for each genre separately from the others. You can accomplish all this with Bookshelves.
A bookshelf is simply a collection of books.You give it a name and tell us which books are part of it, and then it's ready for use. You can use it in the report filters just like you would use a single book. Instead of limiting the report to just the one book, the report will include all books that are on the bookshelf you select.
Books can be in more than one bookshelf, so you can use bookshelves to collect books by series, by language, by format (e-book vs. POD), and/or any other characteristic that makes sense to you.
Click on the "Shelves" tab in the Settings screen to list your bookshelves. You can add a new bookshelf there, specifying which books belong on that shelf. The same book can appear on multiple bookshelves, so you can make bookshelves for different series and also a bookshelf for all your fiction, for example.