This is the first add-on I have found that makes Facebook dark WITHOUT ruining other elements of it. It looks naturally dark as the website intended it.

Dark theme everywhere and effective. Not gonna lie, there are a few pages that will have issues with the color change, but that's really on the pages more than on the extension, the fact that it works so well is an amazing achievement. Some people complain that is not a great extension for reading... but if they read the description they would know that this just to have an ever-present dark theme. For what it does and is supposed to do: 5/5 stars.