Works perfectly with Google calendars. Read the note! Rated 5 out of 5 stars

Lightning is the perfect companion for Thunderbird email management platform. They should be bundled together!Note that Google has recently changed the CaldDAV address, so your Google calendars won't update any more. You can get errors such as "login failed" or "unable to process the event". In any case the solution is as simple as described on this blog post:

This review is for a previous version of the add-on (2.6).