@nyn - it isn't me that opened the can of worms
Come up with whatever the search expression is that is required and I will think about it. In the meantime, I would suggest you just do a saved search with that expression in it - it is just as many clicks to choose that from the saved searches dropdown as it would be to incorporate into this.
My one concern over adding to the plugin is whether it is a little too "bespoke" - if there isn't a specific reason as to why users should care about having an amazon id beyond for completeness sake then it becomes hard to draw the line for other ids as well. For instance why not a check for not having a Goodreads id? Or a Fantastic Fiction id etc. Becomes hard to know where to draw the line once you start doing that, because in all instances there are valid reasons (such as short stories) where your books will not have an ASIN or whatever.
@GeckoFriend - thanks, gald you like