When Jen Allen reviewed book collection management app BookBuddy Pro a couple of years ago, the overall sentiment was that it's a generally helpful app that could've used a few more features. Since that time the folks over at Kimico have been steadily adding to it, resulting in a current version (6.1.2) that addresses the lack of features.
The new BookBuddy Pro now sports a barcode scanner for easy cataloging, improved functions for labeling and finding books in a collection, cloud backups, easy sharing of favorites or entire chunks of a collection, better sorting and organization options, and more. So essentially all of the things we wished were in the app are now in the app.
You can download the latest BookBuddy Pro from the App Store for $4.99, or if you'd rather try before you buy there's also the free version of Book Buddy that comes with a 50 book limit.