Obviously should have ready access to imported data from linked library accounts.
I understand you are set against making ratings public (going against a best practice embraced by every other consumer category in the world), but let us see OUR OWN ratings. We use our own ratings to find new books similar to those we love, and to remind us whether we liked or disliked a book without having to tie it up so others can't read it.
Please use frames in the backend structure. There's a reason they were adopted decades ago across all other websites in the world. Your structure makes it so hard to navigate.
When you show 'similar books' please don't simply show other books by the same author. Those are easily found by clicking author name or searching manually by author. Your mission is to introduce readers to other books and authors they may like.
I should note that I find myself going back use overdrive at individual libraries. That's how bad the ui/ux is on Libby.