I have been using zotero for this purpose. And I know it is absolutely the wrong tool for the job.

But it is pretty good at grabbing the book detail, and I have a bunch of custom fields and comments, and I can add other stuff into the book definition like text files and PDFs and jpgs and URLs.

You can also wholesale share libraries and create group libraries etc. But it is not very good at tracking read and unread status, let alone borrowed and returned. And it definitely doesn't give recommendations.

One of my main difficulties in moving from this to other media libraries is they are all each so focused on one kind of media. I find a lot of the things I want to keep track of, and share, and remember, are mixed media, authors who also paint, or website only books, multi media comics, films, art and literary theory. Not just the things that happen to sit on a shelf that I own. Which database does that music producer / graphic artist / film maker / author sit in my collection?