Select one of two fields AS that field

Looking for the correct way/syntax to select either “isbn-10” or “isbn-13”, depending on which one exists, with preference given to isbn-13 - AS the field name “isbn”.

So, something like this:

SELECT *, isbn-10 OR isbn-13 AS isbn FROM books;

(if both fields are filled (i.e., the row has an isbn-10 entry and an isbn-13 entry), I’d like the isbn-13 field to take precedence - meaning it would be selected instead of isbn-10.