Storing Goodreads ID - internal ID mapping, violation?

[Göran]

We're considering integrating Goodreads into out service, but have a hard time figuring out how to do so without mapping our internal book ID's to Goodreads ID's, but we're afraid this would constitute a breach in TOS, is it?

[Göran]

Still super confused about what is allowed, what is the definition of Goodreads data vs non-goodreads data.
Being able to store a Goodreads ID per book would allow us to not go through the route of search for book, find goodreads id, etc