BISG guidelines for Sets
Summary of BISG guidelines for Sets:
A Set is a snapshot of a Series on a specific date.
Each format of a given Set is assigned a unique ISBN.
A Set’s contents do not change over time.
Each time a given Series is expanded after its initial release, a new Set should created to encompass the new contents.
In layman’s terms, if a product’s contents change, it’s no longer the same product and therefore merits a new SKU/ISBN.