Why I'm Building This
I have used LibraryThing since 2006 to catalog my books. I really love LibraryThing, but Goodreads also has a bunch of handy features, and more of my friends use Goodreads. So I want to catalog and review my books in both places, but entering my books in both places is a hassle. I'm creating this plugin (to be accompanied by a Chrome browser extenssion) to help me sync my book catalog between LibraryThing, Goodreads, and my own WordPress site.
In the process, this plugin is a great way to demonstrate my back-end and front-end WordPress skills, including my experience with various APIs and Gutenberg.
I don't know if anyone else will ever want to use this, but it's something I need, so I'm happy to build it for myself.
My plan for this plugin is to create a book catalog within WordPress which will store and display information about my books. It will include WP-CLI commands to pull books from LibraryThing and Goodreads, and to push books to Goodreads (LibraryThing's API is read-only, so I can't push to LibraryThing). I plan to use those commands to keep LibraryThing and Goodreads in sync.
I also plan to build a Chrome browser extension that will listen for me to create/edit a book in LibraryThing, and then use the WordPress API to create/edit a book in WordPress.
Change of Scope
Goodreads just killed their API, so there goes any hope of integrating with Goodreads.