Search for ebooks across all libraries you have cards for. Repo is split into two parts:
Highlight the name of a book or author on a page and press Cmd+Shift+U to search all your libraries for ebooks related to the selected text via OverDrive/Libby. Or enter your own search terms from the extension popup menu.
Based almost entirely on https://github.com/mdn/webextensions-examples/tree/master/commands.
Go to about:debugging#/runtime/this-firefox choose Load Temporary Add-on and browse to manifest.json
Since extensions aren't available on mobile. Libraries are saved to local storage.