adding edition consisting of few volumes

[Piotr]

How should I add such edition? Should every volume be new edition of same book (which seems without logic) or is there any way marking edition as multi volume(each volume has it's individual isbn)

[gem]

If each volume has its own ISBN, they need to be entered separately into the Goodreads database. There is no way to mark a single edition as encompassing multiple volumes/ISBNs.

Is this a case where the original work was one book, but it was re-released as multiple books, e.g. Part 1, Part 2, etc?

If you provide links to the books/volumes in question, we might be able to give you a more helpful answer.