@kovidgoyal: Using the browser viewer on the quoted book returns an error when clicking "Read":
Code:
Cannot read book
Could not open The Curious Case of Benjamin Button. There was an error while interacting with the database used to store books for offline reading. Click "Show details" for more information.
UnknownError: The operation failed for reasons unrelated to the database itself and not covered by any other error code.
(Using Calibre 5.36 on Linux Mint 20.3)