Goodreads Librarians Group discussion

So, I've recently come upon the problem of volumes. I don't seem to find (if any) recommendations on this issue.
Basically, some editions of different books might be split into volumes. What is the GR policy or practice on adding volumes in the database?
Should we add just one book? Should we add two/+ books (volumes generally have "secondary" ISBNs, which are different, and one "primary" ISBN, which is the same for all volumes)?
How do we combine volumes of an edition with other editions? Or do we?
What about book covers?

I'm bringing this up because:
- Librarian Manual only says "multiple distinct volumes (sold together as a set with one ISBN) "
- I've come across volumes with primary and secondary ISBNs
- I prefer to have one book in the database (and that' how i've done so far)

What do you guys think about this?

How were the books sold originally? As a set, or individually?

the translated edition was originally sold as a set.
as an example: http://www.goodreads.com/search?query... shows the Romanian edition of http://www.goodreads.com/book/show/68...
If you want to buy the book, in any library or online shop, you will get both volumes. Nevertheless, the two volumes also have individual ISBNs, which are probably correct. The publisher's site mentions only one ISBN, different from the individual ones.

If they were sold as a set, they should be listed as a single entity: the set. Regardless of what other information each volume may have.

ok, thank you for clarifying.
It might become interesting if at some point the publisher decides the volumes could be sold separately :D