Books splitted into volumes

[Jakob]

Couldn't find this anywhere...

So, when longer books are published in our language (1000+ pages), they are often splited into volumes.

So I understand that if they're sold together and share ISBN they should have a combined record. (for example this one)

But what when they're sold separately and have different ISBNs?
For example Folletts Kingsbridge trilogy, each book in this trilogy is split into 2 volumes. So we have Book 1, Part 1; Book 1, Part 2; Book 2, Part 1 etc.
Do I just make 2 editons and put them both under Book 1 or how should they be posted?

Thanks

Edit: Found another thread with a similar question...
If I understand correctly, I should add them as new editions to the books under Kingsbridge #1A, and Kingsbridge #1B. And create new books under Kingsbridge #2A and Kingsbridge #2B for the second book.

Should I put them as Kingsbridge #1A or Kingsbridge #1, part 1 like this one?

[Arenda]

Jakob wrote: "If I understand correctly, I should add them as new editions to the books under Kingsbridge #1A, and Kingsbridge #1B. And create new books under Kingsbridge #2A and Kingsbridge #2B for the second book."

Indeed, parts should not be combined with the complete book, and also not with each other. When there are already other editions published in two parts, they should be added as an edition of those, each to the matching book.

Should I put them as Kingsbridge #1A or Kingsbridge #1, part 1 like this one?

I believe both ways are acceptable.

(Note: 1.1 and 1.2 are NOT the correct way to mark partial editions.)