[stvltvs]

Books not published in the US often don't have a LCCN, so not great as a unique ID.

Also if you're actually building a database, never use a meaningful data element like ISBN or LCCN as the primary key. What happens if you have multiple copies, for example?

[PaulHoule]

That's a good point. I should probably print a QR code that is equivalent to a type 4 UUID or a snowflake id and stick it on each individual book. Now that I think of it, I have two copies of Nixon Agonistes which I mentioned in a comment here yesterday.