A series page in reading order
Each series has a page. It should list the books in reading order, which is a number stored on the book.
The list
In the app this list is called Books in this series.
What it says
Take every Book. Per referenced entry, through the Series field: for each series, keep the books that belong to it. Sort by Series order, lowest first.
On the storefront
The map is lists.books-in-series, keyed by series handle. Sorting by Series order is what makes this different from listing the books by hand: add a book with order 4 and it slots in between 3 and 5 without anyone reordering anything.
In your store
Chapters of a course, steps of a kit, issues of a magazine, parts of a set. Give the child type an order number and the parent page sorts itself.