Wow, this is some sad news:
Amazon has shut off the feed that allowed Delicious Library to look up items, unfortunately limiting the app to what users already have (or enter manually).
I wasn’t contacted about this.
I’ve pulled it from the Mac App Store and shut down the website so nobody accidentally buys a non-functional app.
I remember using Delicious Monster with an iSight camera to catalog my paper book library. Pre-ebook days for me.