First, most of the web page is completely broken when using HTTPS, because they're using the css.librarything.com and js.librarything.com domains to serve CSS and JavaScript (without which the site unfortunately doesn't work at all), and the certificate doesn't cover those domains.
Second, I can't submit a message to the Bug Collectors group via the HTTP site, because the JavaScript there is also broken:
Error: $("fp0") is null
Source File: http://js.librarything.com/minified/js/[...].js
Line: 823
Does someone know some way to alert the site admins now?